This file documents the Revision Control System (RCS).
Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation.
Copyright © 1982, 1988, 1989 Walter F. Tichy.
Copyright © 1990, 1991, 1992, 1993, 1994, 1995 Paul Eggert.
Copyright © 1996, 1997 Karl Heinz Marbaise (doing converting job)
This manual(Edition 1.1) documents version 5.7 of the Revision Control System (RCS).
RCS.
RCS.
RCS.
ci.
ci and other RCS commands.
ci.
ci.
co.
co.
co and other RCS commands.
co.
rcs.
rcs.
rcs.
rcs.
rcs.
rcsclean.
rcsclean.
rcsclean.
rcsclean.
rcsdiff.
rcsdiff.
rcsdiff.
rcsdiff.
rcs.
rcs.
rcsmerge.
rcs.
rlog.
rlog.
rlog.
merge.
merge.
merge.
These 'Texinfo' files are hand converted out of the troff/nroff files, which came with the RCS system.
This has done by hand, cause there does not exist a converter which is able to convert (nroff/troff) into GNU's 'Texinfo' format (I know one, which is able to do the other way,'texinfo' to nroff).
The main reason for doing such a stupid work was, to have the opinion to convert the 'Texinfo' into OS/2-IPF format. This conversion is done with "Texinfo converting Tools Release 1.00" which are able to convert to OS/2-IPF format and HTML(not the Perl-script).
The next possibility is to get a well printed manual, using TeX(I use emTeX myself).
This is the first Edition of this manuals, so don't be angry about the cryptic node names within the 'Texinfo' files. That's the only way to have unique node names for alle command line options. And by the way this is the only way to make references to command line options of every command.
The next thing is to make this manual a little more readable, that means not to double subsection with command line options on every command (rlog, rcs, rcsdiff, ···). The way out of this dilemma is to discribe these options within a chapter 'overall options' or 'global options' which can be used on every command(rlog, rcs, rcsdiff···). But this will be done in the next edition, if you like it.
If you like to make a printed manual yourself, you have to TeX it with the 'texinfo' macro package(V2.185), it also works with version 2.150 of the package. It should also work with edition 2 of the 'Texinfo' macro package.
If you found newer versions of troff/nroff manual then please mail to me.
Here are the exact RCS--versions of the troff/roff pages for checking:
$Id: rcs.ms,v 5.4 1995/06/01 16:23:43 eggert Exp $
$Id: ci.1,v 5.17 1995/06/16 06:19:24 eggert Exp $
$Id: co.1,v 5.13 1995/06/01 16:23:43 eggert Exp $
$Id: rcs.1,v 5.13 1995/06/05 08:28:35 eggert Exp $
$Id: ident.1,v 5.4 1993/11/09 17:40:15 eggert Exp $
$Id: rcsclean.1,v 1.12 1993/11/03 17:42:27 eggert Exp $
$Id: rcsdiff.1,v 5.5 1993/11/03 17:42:27 eggert Exp $
$Id: rcsmerge.1,v 5.6 1995/06/01 16:23:43 eggert Exp $
$Id: rlog.1,v 5.9 1995/06/16 06:19:24 eggert Exp $
$Id: merge.1,v 5.7 1995/06/01 16:23:43 eggert Exp $
Also, if you have suggestions for this manual. Changes of chapters, sections and so on.
Do you have good examples for this manual?
Or what else you like.
Please write to me:
Karl Heinz Marbaise KHMarbaise@p69.ks.fido.de Fido-Net: 2:2452/117.69
Walter F. Tichy
Department of Computer Sciences
Purdue University
West Lafayette, Indiana 47907
An important problem in program development and maintenance is version control, i.e., the task of keeping a software system consisting of many versions and configurations well organized. The Revision Control System (RCS) is a software tool that assists with that task. RCS manages revisions of text documents, in particular source programs, documentation, and test data. It automates the storing, retrieval, logging and identification of revisions, and it provides selection mechanisms for composing configurations. This paper introduces basic version control concepts and discusses the practice of version control using RCS. For conserving space, RCS stores deltas, i.e., differences between successive revisions. Several delta storage methods are discussed. Usage statistics show that RCS's delta storage method is space and time efficient. The paper concludes with a detailed survey of version control tools.
Keywords: configuration management, history management, version control, revisions, deltas.
An earlier version of this paper was published in Software--Practice & Experience, 7 (July 1985), 637-654.
Version control is the task of keeping software systems consisting of many versions and configurations well organized. The Revision Control System (RCS) is a set of UNIX commands that assist with that task.
RCS' primary function is to manage revision groups. A revision group is a set of text documents, called revisions, that evolved from each other. A new revision is created by manually editing an existing one. RCS organizes the revisions into an ancestral tree. The initial revision is the root of the tree, and the tree edges indicate from which revision a given one evolved. Besides managing individual revision groups, RCS provides flexible selection functions for composing configurations. RCS may be combined with MAKE (See Feldman), resulting in a powerful package for version control.
RCS also offers facilities for merging updates with customer modifications, for distributed software development, and for automatic identification. Identification is the stamping of revisions and configurations with unique markers. These markers are akin to serial numbers, telling software maintainers unambiguously which configuration is before them.
RCS is designed for both production and experimental environments. In production environments, access controls detect update conflicts and prevent overlapping changes. In experimental environments, where strong controls are counterproductive, it is possible to loosen the controls.
Although RCS was originally intended for programs, it is useful for any text that is revised frequently and whose previous revisions must be preserved. RCS has been applied successfully to store the source text for drawings, VLSI layouts, documentation, specifications, test data, form letters and articles.
This paper discusses the practice of version control using RCS. It also introduces basic version control concepts, useful for clarifying current practice and designing similar systems. Revision groups of individual components are treated in the next three sections, and the extensions to configurations follow. Because of its size, a survey of version control tools appears at the end of the paper.
Suppose a text file f.c is to be placed under control of RCS. Invoking the check-in command
ci f.c
creates a new revision group with the contents of f.c as the initial revision (numbered 1.1) and stores the group into the file f.c,v. Unless told otherwise, the command deletes f.c. It also asks for a description of the group. The description should state the common purpose of all revisions in the group, and becomes part of the group's documentation. All later check-in commands will ask for a log entry, which should summarize the changes made. (The first revision is assigned a default log message, which just records the fact that it is the initial revision.)
Files ending in ,v are called RCS files (v stands for Rersions); the others are called working files. To get back the working file f.c in the previous example, execute the check-out command:
co f.c
This command extracts the latest revision from the revision group
f.c,v and writes it into f.c. The file f.c
can now be edited and, when finished, checked back in with
ci:
ci f.c
Ci assigns number 1.2 to the new revision.
If ci complains with the message
ci error: no lock set by <login>
then the system administrator has decided to configure RCS for a
production environment by enabling the strict locking
feature. If this feature is enabled, all RCS files are
initialized such that check-in operations require a lock on the
previous revision (the one from which the current one evolved).
Locking prevents overlapping modifications if several people work
on the same file. If locking is required, the revision should
have been locked during the check-out by using the option
-l:
co -l f.c
Of course it is too late now for the check-out with locking,
because f.c has already been changed; checking out the
file again would overwrite the modifications. (To prevent
accidental overwrites, co senses the presence of a working
file and asks whether the user really intended to overwrite it.
The overwriting check-out is sometimes useful for backing up to
the previous revision.) To be able to proceed with the check-in
in the present case, first execute
rcs -l f.c
command retroactively locks the latest revision, unless someone else locked it in the meantime. In this case, the two programmers involved have to negotiate whose modifications should take precedence.
If an RCS file is private, i.e., if only the owner of the file is expected to deposit revisions into it, the strict locking feature is unnecessary and may be disabled. If strict locking is disabled, the owner of the RCS file need not have a lock for check-in. For safety reasons, all others still do. Turning strict locking off and on is done with the commands:
rcs -U f.c and rcs -L f.c
These commands enable or disable the strict locking feature for each RCS file individually. The system administrator only decides whether strict locking is enabled initially.
To reduce the clutter in a working directory, all RCS files can
be moved to a subdirectory with the name RCS. RCS commands
look first into that directory for RCS files. All the commands
presented above work with the RCS
subdirectory(1)
It may be undesirable that ci deletes the working file.
For instance, sometimes one would like
to save the current revision, but continue editing. Invoking
ci -l f.c
checks in f.c as usual, but performs an additional
check-out with locking afterwards. Thus, the working file does
not disappear after the check-in. Similarly, the option -u
does a check-in followed by a check-out without locking. This
option is useful if the file is needed for compilation after the
check-in. Both options update the identification markers in the
working file (see below).
Besides the operations ci and co, RCS provides the
following commands:
A synopsis of these commands appears in the Appendix.
RCS can stamp source and object code with special identification strings, similar to product and serial numbers. To obtain such identification, place the marker
$Id$
into the text of a revision, for instance inside a comment. The check-out operation will replace this marker with a string of the form
$Id: filename revisionnumber date time author state locker $
This string need never be touched, because co keeps it
up to date automatically. To propagate the marker into object code,
simply put it into a literal character string.
In C, this is done as follows:
static char rcsid[] = "$Id$";
The command ident extracts such markers from any file,
in particular from object code.
Ident helps to find out which revisions of which modules
were used in a given program. It returns a complete and unambiguous
component list, from which a copy of the program can be reconstructed.
This facility is invaluable for program maintenance.
There are several additional identification markers, one for each component of $Id$. The marker
$Log$
has a similar function. It accumulates the log messages that are requested during check-in. Thus, one can maintain the complete history of a revision directly inside it, by enclosing it in a comment. Figure 1 is an edited version of a log contained in revision 4.1 of the file ci.c. The log appears at the beginning of the file, and makes it easy to determine what the recent modifications were.
/* * $Log: ci.c,v $ * Revision 4.1 1983/05/10 17:03:06 wft * Added option -d and -w, and updated assignment of date, etc. * to new delta. Added handling of default branches. * * Revision 3.9 1983/02/15 15:25:44 wft * Added call to fastcopy() to copy remainder of RCS file. * * Revision 3.8 1983/01/14 15:34:05 wft * Added ignoring of interrupts while new RCS file is renamed; * avoids deletion of RCS files by interrupts. * * Revision 3.7 1982/12/10 16:09:20 wft * Corrected checking of return code from diff. * An RCS file now inherits its mode during the first ci from the * working file, except that write permission is removed. */
Figure 1. Log entries produced by the marker $Log$
Since revisions are stored in the form of differences, each log message is physically stored once, independent of the number of revisions present. Thus, the $Log$ marker incurs negligible space overhead.
RCS arranges revisions in an ancestral tree. The ci
command builds this tree; the auxiliary command rcs prunes
it. The tree has a root revision, normally numbered 1.1, and
successive revisions are numbered 1.2, 1.3, etc. The first field
of a revision number is called the release number and the
second one the level number. Unless given explicitly, the
ci command assigns a new revision number by incrementing
the level number of the previous revision. The release number
must be incremented explicitly, using the -r option of
ci. Assuming there are revisions 1.1, 1.2, and 1.3 in the
RCS file f.c,v, the command
ci -r2.1 f.c or ci -r2 f.c
assigns the number 2.1 to the new revision. Later check-ins
without the -r option will assign the numbers 2.2, 2.3,
and so on. The release number should be incremented only at major
transition points in the development, for instance when a new
release of a software product has been completed.
A young revision tree is slender: It consists of only one branch, called the trunk. As the tree ages, side branches may form. Branches are needed in the following 4 situations.
+-----+ +-----+ +-----+ +-----+ +-----+ ! 1.1 !---->! 1.2 !---->! 1.3 !---->! 2.1 !---->! 2.2 !--->> +-----+ +-----+ +-----+ +-----+ +-----+
Figure 2. A slender revision tree.
co -r1.3 f.c -- check out revision 1.3 edit f.c -- change it ci -r1.3.1 f.c -- check it in on branch 1.3.1
rcsmerge automates this process (see the
Appendix).
+-----+ +-----+ +-----+ +-----+ +-----+
! 1.1 !---->! 1.2 !---->! 1.3 !---->! 2.1 !---->! 2.2 !--->>
+-----+ +-----+ +--+--+ +-----+ +-----+
!
! +---------+
+------->! 1.3.1.1 !---->>
+---------+
Figure 3. A revision tree with one side branch
+-----+ +-----+
--->! 1.3 !---------------->! 2.4 !---->>
+--+--+ +---+-+
! !
! +---------+ ! +---------+
+---->! 1.3.1.1 ! +------>! 2.4.1.1 !
+---------+ +---------+
Figure 4. A customer's revision tree with local modifications.
Sometimes it is desirable to explore an alternate design or a different implementation technique in parallel with the main line development. Such development should be carried out on a side branch. The experimental changes may later be moved into the main line, or abandoned.
A common occurrence is that one programmer has checked out a revision, but cannot complete the assignment for some reason. In the meantime, another person must perform another modification immediately. In that case, the second person should check-out the same revision, modify it, and check it in on a side branch, for later merging.
Every node in a revision tree consists of the following attributes: a revision number, a check-in date and time, the author's identification, a log entry, a state and the actual text. All these attributes are determined at the time the revision is checked in. The state attribute indicates the status of a revision. It is set automatically to `experimental' during check-in. A revision can later be promoted to a higher status, for example `stable' or `released'. The set of states is user-defined.
For conserving space, RCS stores revisions in the form of deltas, i.e., as differences between revisions. The user interface completely hides this fact.
A delta is a sequence of edit commands that transforms one string
into another. The deltas employed by RCS are line-based, which
means that the only edit commands allowed are insertion and
deletion of lines. If a single character in a line is changed,
the edit scripts consider the entire line changed. The program
diff produces a small, line-based delta between pairs of
text files. A character-based edit script would take much longer
to compute, and would not be significantly shorter.
Using deltas is a classical space-time tradeoff: deltas reduce
the space consumed, but increase access time. However, a version
control tool should impose as little delay as possible on
programmers. Excessive delays discourage the use of version
controls, or induce programmers to take shortcuts that compromise
system integrity. To gain reasonably fast access time for both
editing and compiling, RCS arranges deltas in the following way.
The most recent revision on the trunk is stored intact. All other
revisions on the trunk are stored as reverse deltas. A reverse
delta describes how to go backward in the development history: it
produces the desired revision if applied to the successor of that
revision. This implementation has the advantage that extraction
of the latest revision is a simple and fast copy operation.
Adding a new revision to the trunk is also fast: ci simply
adds the new revision intact, replaces the previous revision with
a reverse delta, and keeps the rest of the old deltas. Thus,
ci requires the computation of only one new delta.
Branches need special treatment. The naive solution would be to
store complete copies for the tips of all branches. Clearly, this
approach would cost too much space. Instead, RCS uses
forward deltas for branches. Regenerating a revision on a
side branch proceeds as follows. First, extract the latest
revision on the trunk; secondly, apply reverse deltas until the
fork revision for the branch is obtained; thirdly, apply forward
deltas until the desired branch revision is reached. Figure 5
illustrates a tree with one side branch. Triangles pointing to
the left and right(with five exclamation marks) represent
reverse and forward deltas,
respectively.
! ! ! ! !
+-----! +-----! +-----! +-----! +-----!
! 1.1 !---->! 1.2 !---->! 1.3 !---->! 2.1 !---->! 2.2 !--->>
+-----+ +-----! +--+--! +-----! +-----!
! ! ! ! ! !
!
! ! !
! +---------! +---------!
+->! 1.3.1.1 !---->! 1.3.1.2 !
+---------! +---------!
! !
Figure 3. A revision tree with one side branch
Although implementing fast check-out for the latest trunk revision, this arrangement has the disadvantage that generation of other revisions takes time proportional to the number of deltas applied. For example, regenerating the branch tip in Figure 5 requires application of five deltas (including the initial one). Since usage statistics show that the latest trunk revision is the one that is retrieved in 95 per cent of all cases (see the section on usage statistics), biasing check-out time in favor of that revision results in significant savings. However, careful implementation of the delta application process is necessary to provide low retrieval overhead for other revisions, in particular for branch tips.
There are several techniques for delta application. The naive one
is to pass each delta to a general-purpose text editor. A
prototype of RCS invoked the UNIX editor ed both for
applying deltas and for expanding the identification markers.
Although easy to implement, performance was poor, owing to the
high start-up costs and excess generality of ed. An
intermediate version of RCS used a special-purpose,
stream-oriented editor. This technique reduced the cost of
applying a delta to the cost of checking out the latest trunk
revision. The reason for this behavior is that each delta
application involves a complete pass over the preceding revision.
However, there is a much better algorithm. Note that the deltas
are line oriented and that most of the work of a stream editor
involves copying unchanged lines from one revision to the next. A
faster algorithm avoids unnecessary copying of character strings
by using a piece table. A piece table is a one-dimensional
array, specifying how a given revision is pieced-together
from lines in the RCS file. Suppose piece table PTr
represents revision r. Then PTr[i] contains the
starting position of line i of revision r.
Application of the next delta transforms piece table PTr
into PTr+1. For instance, a delete command removes a
series of entries from the piece table. An insertion command
inserts new entries, moving the entries following the insertion
point further down the array. The inserted entries point to the
text lines in the delta. Thus, no I/O is involved except for
reading the delta itself. When all deltas have been applied to
the piece table, a sequential pass through the table looks up
each line in the RCS file and copies it to the output file,
updating identification markers at the same time. Of course, the
RCS file must permit random access, since the copied lines are
scattered throughout that file. Figure 6 illustrates an RCS file
with two revisions and the corresponding piece tables.
The piece table approach has the property that the time for applying a single delta is roughly determined by the size of the delta, and not by the size of the revision. For example, if a delta is 10 per cent of the size of a revision, then applying it takes only 10 per cent of the time to generate the latest trunk revision. (The stream editor would take 100 per cent.)
There is an important alternative for representing deltas that
affects performance. SCCS, a precursor of RCS, uses
interleaved deltas. A file containing interleaved deltas
is partitioned into blocks of lines. Each block has a header that
specifies to which revision(s) the block belongs. The blocks are
sorted out in such a way that a single pass over the file can
pick up all the lines belonging to a given revision. Thus, the
regeneration time for all revisions is the same: all headers must
be inspected, and the associated blocks either copied or skipped.
As the number of revisions increases, the cost of retrieving any
revision is much higher than the cost of checking out the latest
trunk revision with reverse deltas. A detailed comparison of
SCCS's interleaved deltas and RCS's reverse deltas can be
found in Reference 4. This reference considers the version of RCS
with the stream editor only. The piece table method improves
performance further, so that RCS is always faster than SCCS,
except if 10 or more deltas are applied.
Additional speed-up for both delta methods can be obtained by
caching the most recently generated revision, as has been
implemented in DSEE With caching, access time to
frequently used revisions can approach normal file access time,
at the cost of some additional space.
The locking mechanism for RCS was difficult to design. The problem and its solution are first presented in their pure form, followed by a discussion of the complications caused by real-world considerations.
RCS must prevent two or more persons from depositing competing
changes of the same revision. Suppose two programmers check out
revision 2.4 and modify it. Programmer A checks in a revision
before programmer B. Unfortunately, programmer B has not seen
A's changes, so the effect is that A's changes are covered up by
B's deposit. A's changes are not lost since all revisions are
saved, but they are confined to a single revision(2)
This conflict is prevented in RCS by locking. Whenever someone
intends to edit a revision (as opposed to reading or compiling
it), the revision should be checked out and locked, using the
-l option on co. On subsequent check-in, ci
tests the lock and then removes it. At most one programmer at a
time may lock a particular revision, and only this programmer may
check in the succeeding revision. Thus, while a revision is
locked, it is the exclusive responsibility of the locker.
An important maxim for software tools like RCS is that they must not stand in the way of making progress with a project. This consideration leads to several weakenings of the locking mechanism. First of all, even if a revision is locked, it can still be checked out. This is necessary if other people wish to compile or inspect the locked revision while the next one is in preparation. The only operations they cannot do are to lock the revision or to check in the succeeding one. Secondly, check-in operations on other branches in the RCS file are still possible; the locking of one revision does not affect any other revision. Thirdly, revisions are occasionally locked for a long period of time because a programmer is absent or otherwise unable to complete the assignment. If another programmer has to make a pressing change, there are the following three alternatives for making progress:
If an RCS file is private, i.e., when a programmer owns an RCS file and does not expect anyone else to perform check-in operations, locking is an unnecessary nuisance. In this case, the strict locking feature discussed earlier may be disabled, provided that file protection is set such that only the owner may write the RCS file. This has the effect that only the owner can check-in revisions, and that no lock is needed for doing so.
As added protection, each RCS file contains an access list that
specifies the users who may execute update operations. If an
access list is empty, only normal UNIX file protection applies.
Thus, the access list is useful for restricting the set of people
who would otherwise have update permission. Just as with
locking, the access list has no effect on read-only operations
such as co. This approach is consistent with the UNIX
philosophy of openness, which contributes to a productive
software development environment.
The preceding sections described how RCS deals with
revisions of individual components; this section discusses how to
handle configurations. A configuration is a set of revisions,
where each revision comes from a different revision group, and
the revisions are selected according to a certain criterion. For
example, in order to build a functioning compiler, the `right'
revisions from the scanner, the parser, the optimizer and the
code generator must be combined. RCS, in conjunction with
MAKE, provides a number of facilities to effect a smooth
selection.
co command
makes this selection by default. For example, the command
co *,v
retrieves the latest revision on the default branch of each RCS file in the current directory. The default branch is usually the trunk, but may be set to be a side branch. Side branches as defaults are needed in distributed software development, as discussed in the section on the RCS revision tree.
co -r2 *,v
retrieves the latest revision with release number 2 from each RCS file. This selection is convenient if a release has been completed and development has moved on to the next release.
co -r2 -sReleased *,v
retrieves the latest revision with release number 2 whose state
attribute is `Released'. Of course, the state attribute has to be
set appropriately, using the ci or rcs commands.
Another alternative is to select a revision by its author, using
the -w option.
co -d'March 4, 1:00 pm LT' *,v
checks out all the components of that release, independent of the
numbering. The -d option specifies a `cutoff date', i.e.,
the revision selected has a check-in date that is closest to, but
not after the date given.
co command will not suffice to select the right revisions.
Symbolic revision numbers solve this problem. Each RCS file may
contain a set of symbolic names that are mapped to numeric
revision numbers. For example, assume the symbol V3 is
bound to release number 2 in file s,v, and to revision
number 15.9 in t,v. Then the single command
co -rV3 s,v t,v
retrieves the latest revision of release 2 from s,v, and revision 15.9 from t,v. In a large system with many modules, checking out all revisions with one command greatly simplifies configuration management.
Judicious use of symbolic revision numbers helps with organizing large configurations.
A special command, rcsfreeze, assigns a symbolic revision
number to a selected revision in every RCS file. rcsfreeze
effectively freezes a configuration. The assigned symbolic
revision number selects all components of the configuration. If
necessary, symbolic numbers may even be intermixed with numeric
ones. Thus, V3.5 in the above example would select
revision 2.5 in s,v and branch 15.9.5 in t,v.
The options -r, -s, -w and -d may be
combined. If a branch is given, the latest revision on that
branch satisfying all conditions is retrieved; otherwise, the
default branch is used.
MAKE (Feldman) is a program that processes configurations. It is driven by configuration specifications recorded in a special file, called a `Makefile'. MAKE avoids redundant processing steps by comparing creation dates of source and processed objects. For example, when instructed to compile all modules of a given system, it only recompiles those source modules that were changed since they were processed last.
MAKE has been extended with an auto-checkout
feature(3)RCS for needed files, rather than just the current working
directory. However, if a working file is present, MAKE totally
ignores the corresponding RCS file and uses the working file. (In
newer versions of MAKE distributed by AT&T and others,
auto-checkout can be achieved with the rule DEFAULT, instead of a
special extension of MAKE. However, a file checked out by the
rule DEFAULT will not be deleted after processing.
Rcsclean can be used for that purpose.)
With auto-checkout, RCS/MAKE can effect a selection rule especially tuned for multi-person software development and maintenance. In these situations, programmers should obtain configurations that consist of the revisions they have personally checked out plus the latest checked in revision of all other revision groups. This schema can be set up as follows.
Each programmer chooses a working directory and places into it a
symbolic link, named RCS, to the directory containing the
relevant RCS files. The symbolic link makes sure that co
and ci operations need only specify the working files, and
that the Makefile need not be changed. The programmer then checks
out the needed files and modifies them. If MAKE is invoked, it
composes configurations by selecting those revisions that are
checked out, and the rest from the subdirectory RCS. The
latter selection may be controlled by a symbolic revision number
or any of the other selection criteria. If there are several
programmers editing in separate working directories, they are
insulated from each other's changes until checking in their
modifications.
Similarly, a maintainer can recreate an older configuration by starting to work in an empty working directory. During the initial MAKE invocation, all revisions are selected from RCS files. As the maintainer checks out files and modifies them, a new configuration is gradually built up. Every time MAKE is invoked, it substitutes the modified revisions into the configuration being manipulated.
A final application of RCS is to use it for storing Makefiles.
Revision groups of Makefiles represent multiple versions of
configurations. Whenever a configuration is baselined or
distributed, the best approach is to unambiguously fix the
configuration with a symbolic revision number by calling
rcsfreeze, to embed that symbol into the Makefile, and to
check in the Makefile (using the same symbolic revision number).
With this approach, old configurations can be regenerated easily
and reliably.
The following usage statistics were collected on two DEC VAX-11/780 computers of the Purdue Computer Science Department. Both machines are mainly used for research purposes. Thus, the data reflect an environment in which the majority of projects involve prototyping and advanced software development, but relatively little long-term maintenance.
For the first experiment, the ci and co operations
were instrumented to log the number of backward and forward
deltas applied. The data were collected during a 13 month period
from Dec. 1982 to Dec. 1983. Table I summarizes the results.
Oper. ! Total !Total deltas!mean deltas! Operations !Branch
!operations! applied ! applied !with >1 delta!operations
-------+----------+------------+-----------+-------------+----------
co ! 7867 ! 9320 ! 1.18 ! 509 (6%) ! 203 (3%)
ci ! 3468 ! 2207 ! 0.64 ! 85 (2%) ! 75 (2%)
ci & co! 11335 ! 11527 ! 1.02 ! 594 (5%) ! 278 (2%)
Table I. Statistics for co and ci operations
The first two lines show statistics for check-out and check-in;
the third line shows the combination. Recall that ci
performs an implicit check-out to obtain a revision for computing
the delta. In all measures presented, the most recent revision
(stored intact) counts as one delta. The number of deltas
applied represents the number of passes necessary, where the
first `pass' is a copying step.
Note that the check-out operation is executed more than twice as
frequently as the check-in operation. The fourth column gives the
mean number of deltas applied in all three cases. For ci,
the mean number of deltas applied is less than one. The reasons
are that the initial check-in requires no delta at all, and that
the only time ci requires more than one delta is for
branches. Column 5 shows the actual number of operations that
applied more than one delta. The last column indicates that
branches were not used often.
The last three columns demonstrate that the most recent trunk
revision is by far the most frequently accessed. For RCS,
check-out of this revision is a simple copy operation, which is
the absolute minimum given the copy-semantics of co.
Access to older revisions and branches is more common in
non-academic environments, yet even if access to older deltas
were an order of magnitude more frequent, the combined average
number of deltas applied would still be below 1.2. Since RCS is
faster than SCCS until up to 10 delta applications, reverse
deltas are clearly the method of choice. .PP The second
experiment, conducted in March of 1984, involved surveying the
existing RCS files on our two machines. The goal was to
determine the mean number of revisions per RCS file, as well as
the space consumed by them. Table II shows the results. (Tables I
and II were produced at different times and are unrelated.)
!Total RCS! Total !Mean !Means size!Mean size!Overhead
! files !revisions!revisions!RCS files !revisions!
----------+---------+---------+---------+----------+---------+--------
All Files ! 8033 ! 11133 ! 1.39 ! 6156 ! 5585 ! 1.10
Files with! 1477 ! 4578 ! 3.10 ! 8074 ! 6041 ! 1.34
>= 2 delta! ! ! ! ! !
Table II. Statistics for RCS files
In our sample, over 80 per cent of the RCS files contained only a single revision. The reason is that our systems programmers routinely check in all source files on the distribution tapes, even though they may never touch them again. To get a better indication of how much space savings are possible with deltas, all measures with those files that contained 2 or more revisions were recomputed. Only for those files is RCS necessary. As shown in the second line, the average number of revisions for those files is 3.10, with an overhead of 1.34. This means that the extra 2.10 deltas require 34 per cent extra space, or 16 per cent per extra revision. Rochkind(Rochkind) measured the space consumed by SCCS, and reported an average of 5 revisions per group and an overhead of 1.37 (or about 9 per cent per extra revision). In a later paper, Glasser (Glasser) observed an average of 7 revisions per group in a single, large project, but provided no overhead figure. In his paper on DSEE , Leblang (Leblang) reported that delta storage combined with blank compression results in an overhead of a mere 1-2 per cent per revision. Since leading blanks accounted for about 20 per cent of the surveyed Pascal programs, a revision group with 5-10 members was smaller than a single cleartext copy.
The above observations demonstrate clearly that the space needed for extra revisions is small. With delta storage, the luxury of keeping multiple revisions online is certainly affordable. In fact, introducing a system with delta storage may reduce storage requirements, because programmers often save back-up copies anyway. Since back-up copies are stored much more efficiently with deltas, introducing a system such as RCS may actually free a considerable amount of space.
The need to keep back-up copies of software arose when programs and data were no longer stored on paper media, but were entered from terminals and stored on disk. Back-up copies are desirable for reliability, and many modern editors automatically save a back-up copy for every file touched. This strategy is valuable for short-term back-ups, but not suitable for long-term version control, since an existing back-up copy is overwritten whenever the corresponding file is edited.
Tape archives are suitable for long-term, offline storage. If all changed files are dumped on a back-up tape once per day, old revisions remain accessible. However, tape archives are unsatisfactory for version control in several ways. First, backing up the file system every 24 hours does not capture intermediate revisions. Secondly, the old revisions are not online, and accessing them is tedious and time-consuming. In particular, it is impractical to compare several old revisions of a group, because that may require mounting and searching several tapes. Tape archives are important fail-safe tools in the event of catastrophic disk failures or accidental deletions, but they are ill-suited for version control. Conversely, version control tools do not obviate the need for tape archives.
A natural technique for keeping several old revisions online is to never delete a file. Editing a file simply creates a new file with the same name, but with a different sequence number. This technique, available as an option in DEC's VMS operating system, turns out to be inadequate for version control. First, it is prohibitively expensive in terms of storage costs, especially since no data compression techniques are employed. Secondly, indiscriminately storing every change produces too many revisions, and programmers have difficulties distinguishing them. The proliferation of revisions forces programmers to spend much time on finding and deleting useless files. Thirdly, most of the support functions like locking, logging, revision selection, and identification described in this paper are not available.
An alternative approach is to separate editing from revision
control. The user may repeatedly edit a given revision, until
freezing it with an explicit command. Once a revision is frozen,
it is stored permanently and can no longer be modified. (In RCS,
freezing a revisions is done with ci.) Editing a frozen
revision implicitly creates a new one, which can again be changed
repeatedly until it is frozen itself. This approach saves exactly
those revisions that the user considers important, and keeps the
number of revisions manageable. IBM's CLEAR/CASTER (Brown),
AT&T's SCCS (Rochkind), CMU's SDC (Habermann), and
DEC's CMS (DEC), are examples of version control systems
using this approach. CLEAR/CASTER maintains a data base of
programs, specifications, documentation and messages, using
deltas. Its goal is to provide control over the development
process from a management viewpoint. SCCS stores multiple
revisions of source text in an ancestral tree, records a log
entry for each revision, provides access control, and has
facilities for uniquely identifying each revision. An efficient
delta technique reduces the space consumed by each revision
group. SDC is much simpler than SCCS because it stores not more
than two revisions. However, it maintains a complete log for all
old revisions, some of which may be on back-up tape. CMS, like
SCCS, manages tree-structured revision groups, but offers no
identification mechanism.
Tools for dealing with configurations are still in a state of flux. SCCS, SDC and CMS can be combined with MAKE or MAKE-like programs. Since flexible selection rules are missing from all these tools, it is sometimes difficult to specify precisely which revision of each group should be passed to MAKE for building a desired configuration. The Xerox Cedar system (Lampson) provides a `System Modeller' that can rebuild a configuration from an arbitrary set of module revisions. The revisions of a module are only distinguished by creation time, and there is no tool for managing groups. Since the selection rules are primitive, the System Modeller appears to be somewhat tedious to use. Apollo's DSEE (Leblang) is a sophisticated software engineering environment. It manages revision groups in a way similar to SCCS and CMS. Configurations are built using `configuration threads'. A configuration thread states which revision of each group named in a configuration should be chosen. A configuration thread may contain dynamic specifiers (e.g., `choose the revisions I am currently working on, and the most recent revisions otherwise'), which are bound automatically at build time. It also provides a notification mechanism for alerting maintainers about the need to rebuild a system after a change.
RCS is based on a general model for describing multi-version/multi-configuration systems (Tichy1). The model describes systems using AND/OR graphs, where AND nodes represent configurations, and OR nodes represent version groups. The model gives rise to a suit of selection rules for composing configurations, almost all of which are implemented in RCS. The revisions selected by RCS are passed to MAKE for configuration building. Revision group management is modelled after SCCS. RCS retains SCCS's best features, but offers a significantly simpler user interface, flexible selection rules, adequate integration with MAKE and improved identification. A detailed comparison of RCS and SCCS appears in Reference 4.
An important component of all revision control systems is a
program for computing deltas. SCCS and RCS use the program
diff (Rochkind), which first computes the longest
common substring of two revisions, and then produces the delta
from that substring. The delta is simply an edit script
consisting of deletion and insertion commands that generate one
revision from the other.
A delta based on a longest common substring is not necessarily minimal, because it does not take advantage of crossing block moves. Crossing block moves arise if two or more blocks of lines (e.g., procedures) appear in a different order in two revisions. An edit script derived from a longest common substring first deletes the shorter of the two blocks, and then reinserts it. Heckel (Heckel) proposed an algorithm for detecting block moves, but since the algorithm is based on heuristics, there are conditions under which the generated delta is far from minimal. DSEE uses this algorithm combined with blank compression, apparently with satisfactory overall results. A new algorithm that is guaranteed to produce a minimal delta based on block moves appears in Reference 13. A future release of RCS will use this algorithm.
Acknowledgements:
Many people have helped make RCS a success by contributed criticisms, suggestions, corrections, and even whole new commands (including manual pages). The list of people is too long to be reproduced here, but my sincere thanks for their help and goodwill goes to all of them.
The Revision Control System (RCS) manages multiple revisions of files. RCS automates the storing, retrieval, logging, identification, and merging of revisions. RCS is useful for text that is revised frequently, for example programs, documentation, graphics, papers, and form letters.
The basic user interface is extremely simple. The novice
only needs to learn two commands: ci and co.
ci, short for "check in", deposits the contents of a file into
an archival file called an RCS file.
An RCS file contains all revisions of a particular file.
co, short for "check out",
retrieves revisions from an RCS file.
mkdir RCS
Then invoke the check-in command
ci f.c
This command creates an RCS file in the RCS directory, stores f.c into it as revision 1.1, and deletes f.c. It also asks you for a description. The description should be a synopsis of the contents of the file. All later check-in commands will ask you for a log entry, which should summarize the changes that you made.
Files in the RCS directory are called RCS files; the others are called working files. To get back the working file f.c in the previous example, use the check-out command
co f.c
This command extracts the latest revision from the RCS file and writes it into f.c. If you want to edit f.c, you must lock it as you check it out with the command
co -l f.c
You can now edit f.c.
Suppose after some editing you want to know what changes that you have made. The command
rcsdiff f.c
tells you the difference between the most recently checked-in version and the working file. You can check the file back in by invoking
ci f.c
This increments the revision number properly.
If ci complains with the message
ci error: no lock set by your name
then you have tried to check in a file even though you did not lock it when you checked it out. Of course, it is too late now to do the check-out with locking, because another check-out would overwrite your modifications. Instead, invoke
rcs -l f.c
This command will lock the latest revision for you, unless somebody else got ahead of you already. In this case, you'll have to negotiate with that person.
Locking assures that you, and only you, can check in the
next update, and avoids nasty problems if several people
work on the same file. Even if a revision is locked, it
can still be checked out for reading, compiling, etc. All
that locking prevents is a check-in by anybody but the
locker.
If your RCS file is private, i.e., if you are the only person who is going to deposit revisions into it, strict locking is not needed and you can turn it off. If strict locking is turned off, the owner of the RCS file need not have a lock for check-in; all others still do. Turning strict locking off and on is done with the commands
rcs -U f.c and rcs -L f.c
If you don't want to clutter your working directory with RCS files, create a subdirectory called RCS in your work- ing directory, and move all your RCS files there. RCS commands will look first into that directory to find needed files. All the commands discussed above will still work, without any modification. (Actually, pairs of RCS and working files can be specified in three ways: (a) both are given, (b) only the working file is given, (c) only the RCS file is given. Both RCS and working files may have arbitrary path prefixes; RCS commands pair them up intelligently.)
To avoid the deletion of the working file during check-in (in case you want to continue editing or compiling), invoke
ci -l f.c or ci -u f.c
These commands check in f.c as usual, but perform an implicit check-out. The first form also locks the checked in revision, the second one doesn't. Thus, these options save you one check-out operation. The first form is useful if you want to continue editing, the second one if you just want to read the file. Both update the identification markers in your working file (see below).
You can give ci the number you want assigned to a checked in revision. Assume all your revisions were numbered 1.1, 1.2, 1.3, etc., and you would like to start release 2. The command
ci -r2 f.c or ci -r2.1 f.c
assigns the number 2.1 to the new revision. From then on, ci will number the subsequent revisions with 2.2, 2.3, etc. The corresponding co commands
co -r2 f.c and co -r2.1 f.c
retrieve the latest revision numbered 2.x and the revision
2.1, respectively. co without a revision number selects
the latest revision on the trunk, i.e. the highest revision
with a number consisting of two fields. Numbers with
more than two fields are needed for branches. For example,
to start a branch at revision 1.3, invoke
ci -r1.3.1 f.c
This command starts a branch numbered 1 at revision 1.3, and assigns the number 1.3.1.1 to the new revision. For more information about branches, see rcsOptb.
RCS can put special strings for identification into your source and object code. To obtain such identification, place the marker
$Id$
into your text, for instance inside a comment. RCS will replace this marker with a string of the form
$Id: filename revision date time author state $
With such a marker on the first page of each module, you can always see with which revision you are working. RCS keeps the markers up to date automatically. To propagate the markers into your object code, simply put them into literal character strings. In C, this is done as follows:
static char rcsid[] = "$Id$";
The command ident extracts such markers from any file, even object code and dumps. Thus, ident lets you find out which revisions of which modules were used in a given program.
You may also find it useful to put the marker $Log$ into your text, inside a comment. This marker accumulates the log messages that are requested during check-in. Thus, you can maintain the complete history of your file directly inside it. There are several additional identification markers; see coKeyword for details.
Ci stores the contents of a working file into the
corresponding RCS file as a new revision.
If the RCS file doesn't exist, ci creates it.
Ci removes the working file, unless one of the options
-u or -l is present.
For each check-in, ci asks for a commentary
describing the changes relative to the previous revision.
Ci assigns the revision number given by the -r option;
if that option is missing, it derives the number from the
lock held by the user; if there is no lock and locking is not strict,
ci increments the number of the latest revision on the trunk.
A side branch can only be started by explicitly specifying its
number with the -r option during check-in.
Ci also determines whether the revision to be checked in is
different from the previous one, and asks whether to proceed if not.
This facility simplifies check-in operations for large systems,
because one need not remember which files were changed.
The option -k searches the checked in file for identification
markers containing the attributes
revision number, check-in date, author and state, and assigns these
to the new revision rather than computing them. This option is
useful for software distribution: Recipients of distributed software
using RCS should check in updates with the -k option.
This convention guarantees that revision numbers, check-in dates,
etc., are the same at all sites.
Co retrieves revisions according to revision number,
date, author and state attributes. It either places the revision
into the working file, or prints it on the standard output.
Co always expands the identification markers.
Ident extracts the identification markers expanded by co
from any file and prints them.
Rcsis an administrative operation that changes access lists,
locks, unlocks, breaks locks, toggles the strict-locking feature,
sets state attributes and symbolic revision numbers, changes the
description, and deletes revisions. A revision can
only be deleted if it is not the fork of a side branch.
Rcsclean removes working files that were checked out but never changed.
(4)rcsclean and rcsfreeze commands are optional
and are not always installed.Rcsdiff compares two revisions and prints their
difference, using the UNIX tool diff.
One of the revisions compared may be checked out.
This command is useful for finding out about changes.
Rcsfreeze assigns the same symbolic revision number
to a given revision in all RCS files.
This command is useful for accurately recording a configuration.
Rcsmerge merges two revisions, rev1 and rev2,
with respect to a common ancestor.
A 3-way file comparison determines the segments of lines that
are (a) the same in all three revisions, or (b) the same in 2 revisions,
or (c) different in all three. For all segments of type (b) where
rev1 is the differing revision,
the segment in rev1 replaces the corresponding segment of rev2.
Type (c) indicates an overlapping change, is flagged as an error, and requires user
intervention to select the correct alternative.
Rlog prints the log messages and other information in an RCS file.
ci.
ci.
ci and other RCS commands.
ci.
ci stores new revisions into RCS files. Each pathname
matching an RCS suffix is taken to be an RCS file. All others are
assumed to be working files containing new revisions. ci
deposits the contents of each working file into the corresponding
RCS file. If only a working file is given, ci tries to
find the corresponding RCS file in an RCS subdirectory and then
in the working file's directory. For more details, See ciFileNaming
below.
For ci to work, the caller's login must be on the access
list, except if the access list is empty or the caller is the
superuser or the owner of the file. To append a new revision to
an existing branch, the tip revision on that branch must be
locked by the caller. Otherwise, only a new branch can be
created. This restriction is not enforced for the owner of the
file if non-strict locking is used (see rcs). A lock held
by someone else can be broken with the rcs command.
Unless the -f option is given, ci checks whether
the revision to be deposited differs from the preceding one. If
not, instead of creating a new revision ci reverts to the
preceding one. To revert, ordinary ci removes the working
file and any lock; ci -l keeps and ci -u
removes any lock, and then they both generate a new working file
much as if co -l or co -u had been applied to
the preceding revision. When reverting, any -n and
-s options apply to the preceding revision.
For each revision deposited, ci prompts for a log message.
The log message should summarize the change and must be
terminated by end-of-file or by a line containing . by
itself. If several files are checked in ci asks whether to
reuse the previous log message. If the standard input is not a
terminal, ci suppresses the prompt and uses the same log
message for all files(Option -m of ci, ciOptm).
If the RCS file does not exist, ci creates it and deposits
the contents of the working file as the initial revision (default
number: 1.1 ). The access list is initialized to empty.
Instead of the log message,
ci requests descriptive text
(Option -t of ci, ciOptt)
below).
The number rev of the deposited revision can be given by any
of the options -f, -i, -I, -j,
-k, -l, -M, -q, -r or -u
rev can be symbolic, numeric, or mixed.
Symbolic names in
rev must already be defined;
see the Option -n (ciOptn) and -N (ciOptNu)
options for assigning names during checkin.
If rev is $, ci determines the revision
number from keyword values in the working file.
If rev begins with a period, then the default branch
(normally the trunk) is prepended to it. If rev is a
branch number followed by a period, then the latest revision on
that branch is used.
If rev is a revision number, it must be higher than the
latest one on the branch to which rev belongs, or must
start a new branch.
If rev is a branch rather than a revision number, the new
revision is appended to that branch. The level number is
obtained by incrementing the tip revision number of that branch.
If rev indicates a non-existing branch, that branch is
created with the initial revision numbered rev .1.
If rev is omitted, ci tries to derive the new
revision number from the caller's last lock. If the caller has
locked the tip revision of a branch, the new revision is appended
to that branch. The new revision number is obtained by
incrementing the tip revision number. If the caller locked a
non-tip revision, a new branch is started at that revision by
incrementing the highest branch number at that revision. The
default initial branch and level numbers are 1..
If rev is omitted and the caller has no lock, but owns the
file and locking is not set to strict, then the revision
is appended to the default branch (normally the trunk; see the
option -b of rcs rcsOptb).
Exception: On the trunk, revisions can be appended to the end, but not inserted.
Overview off all options which can be given to
Synopsis: ci [options] file ···
ci.
-r option (without any revision) has an unusual
meaning in ci. With other RCS commands, a bare -r
option specifies the most recent revision on the default branch,
but with ci, a bare -r option reestablishes the
default behavior of releasing a lock and removing the working
file, and is used to override any default -l or -u
options established by shell aliases or scripts.
-r, except it performs an additional
co-l for the deposited revision. Thus, the
deposited revision is immediately checked out again and
locked. This is useful for saving a revision although
one wants to continue editing it after the checkin.
-l, except that the deposited revision is not
locked. This lets one read the working file immediately after
checkin.
The -l, bare -r, and -u options are mutually
exclusive and silently override each other. For example, ci
-u -r is equivalent to ci -r because bare -r
overrides -u.
-k option at these sites to preserve
the original number, date, author, and state. The extracted
keyword values and the default log message can be overridden with
the options -d, -m, -s, -w, and any
option that carries a revision number.
-f is given.
date for the checkin date and time. The date
is specified in free format as explained in co (See CheckOut).
This is useful for lying about the checkin date, and for -k if
no date is available. If date is empty, the working file's
time of last modification is used.
ci -d -M -u f does
not alter f 's modification time, even if f's
contents change due to keyword substitution. Use this option with
care; it can confuse MAKE.
msg as the log message for all revisions
checked in. By convention, log messages that start with #
are comments and are ignored by programs like GNU Emacs's
vc package. Also, log messages that start with
{ clumpname } (followed by white space) are meant to be
clumped together if possible, even if they are associated with
different files; the { clumpname } label is used only
for clumping, and is not considered to be part of the log message
itself.
name to the number of the
checked-in revision. ci prints an error message if
name is already assigned to another number.
-n, except that it overrides a previous assignment
of name.
state. The default state is Exp.
-.
The -t option, in both its forms, has effect only during
an initial checkin; it is silently ignored otherwise.
During the initial checkin, if -t is not given, ci
obtains the text from standard input, terminated by end-of-file
or by a line containing . by itself. The user is prompted
for the text if interaction is possible; see optiom -I
of ci(See ciOptIu).
For backward compatibility with older versions of RCS, a bare
-t option is ignored.
ci usually updates the RCs file's
modification time to the current time, because the lock is stored
in the RCS file and removing the lock requires changing the RCS
file. This can create an RCS file newer than the working file in
one of two ways: first, ci -M can create a working file
with a date before the current time; second, when reverting to
the previous revision the RCS file can change while the working
file remains unchanged. These two cases can cause excessive
recompilation caused by a MAKE dependency of the working
file on the RCS file. The -T option inhibits this
recompilation by lying about the RCS file's date. Use this option
with care; it can suppress recompilation even when a checkin of
one working file should affect another working file associated
with the same RCS file. For example, suppose the RCS file's time
is 01:00, the (changed) working file's time is 02:00, some other
copy of the working file has a time of 03:00, and the current
time is 04:00. Then ci -d -T sets the RCS file's time to
02:00 instead of the usual 04:00; this causes MAKE to
think (incorrectly) that the other copy is newer than the RCs
file.
login for the author field of the deposited revision.
Useful for lying about the author, and for -k if no author
is available.
n. See coOptV
RCS/path or
path1/RCS/path2. The -x option can specify a list
of suffixes separated by . For example, -x,v/
specifies two suffixes: ,v and the empty suffix. If two or
more suffixes are specified, they are tried in order when looking
for an RCS file; the first one that works is used for that file.
If no RCS file is found but an RCS file can be created, the
suffixes are tried in order to determine the new RCS file's name.
The default for suffixes is installation-dependent;
normally it is ,v/ for hosts like Unix that permit commas
in filenames, and is empty (i.e. just the empty suffix) for other
hosts.
date in the
-ddate option. The zoone should be empty, a
numeric UTC offset, or the special string LT for local
time. The default is an empty zoone, which uses the
traditional RCS format of UTC without any time zone indication and
with slashes separating the parts of the date; otherwise, times
are output in ISO 8601 format with time zone indication. For
example, if local time is January 11, 1990, 8pm Pacific Standard
Time, eight hours west of UTC, then the time is output as
follows:
Optiontime output-z1990/01/11 04:00:00(default)-zLT1990-01-11 20:00:00-0800-z+05301990-01-11 09:30:00+0530
This option does not affect dates stored in RCS files, which are always UTC.
Pairs of RCS files and working files can be specified in three ways (see also the example section).
path1/workfileX
and the working pathname is of the form
path2/workfile where path1/ and path2/
are (possibly different or empty) paths, workfile
is a filename, and X is an RCs suffix. If X
is empty, path1/ must start with RCS/ or
must contain /RCS/.
path1/ and the suffix X.
ci considers each
X in turn, looking for an RCS file of the form
path2/RCS/workfileX or (if the former is not found and
X is nonempty) path2/workfileX.
If the RCS file is specified without a path in 1) and 2),
ci looks for the RCS file first in the directory
./RCS and then in the current directory.
ci reports an error if an attempt to open an RCS file
fails for an unusual reason, even if the RCS file's pathname is
just one of several possibilities. For example, to suppress use
of RCS commands in a directory d , create a regular file
named d/RCS so that casual attempts to use RCS commands in
d fail because d/RCS is not a directory.
Suppose ,v is an RCS suffix and the current directory
contains a subdirectory RCS with an RCS file
io.c,v. Then each of the following commands check in a
copy of io.c into RCS/io.c,v as the latest
revision, removing io.c.
ci io.c ci RCS/io.c,v ci io.c,v ci io.c RCS/io.c,v ci io.c io.c,v ci RCS/io.c,v io.c ci io.c,v io.c
Suppose instead that the empty suffix is an RCS suffix and the
current directory contains a subdirectory RCS with an RCS
file io.c. The each of the following commands checks in a
new revision.
ci io.c ci RCS/io.c ci io.c RCS/io.c ci RCS/io.c io.c
An RCS file created by ci inherits the read and execute
permissions from the working file. If the RCS file exists
already, ci preserves its read and execute permissions.
ci always turns off all write permissions of RCS files.
Temporary files are created in the directory containing the
working file, and also in the temporary directory (See ciEnv
under coEnv). A semaphore file or files
are created in the directory containing the RCS file. With a
nonempty suffix, the semaphore names begin with the first
character of the suffix; therefore, do not specify an suffix
whose first character could be that of a working filename. With
an empty suffix, the semaphore names end with _ so working
filenames should not end in _
ci never changes an RCS or working file. Normally,
ci unlinks the file and creates a new one; but instead of
breaking a chain of one or more symbolic links to an RCS file, it
unlinks the destination file instead. Therefore, ci breaks
any hard or symbolic links to any working file it changes; and
hard links to RCS files are ineffective, but symbolic links to
RCS files are preserved.
The effective user must be able to search and write the directory
containing the RCS file. Normally, the real user must be able to
read the RCS and working files and to search and write the
directory containing the working file; however, some older hosts
cannot easily switch between real and effective users, so on
these hosts the effective user is used for all accesses. The
effective user is the same as the real user unless your copies of
ci and co have setuid privileges. As described in
the next section, these privileges yield extra security if the
effective user owns all RCS files and directories, and if only
the effective user can write RCS directories.
Users can control access to RCS files by setting the permissions of the directory containing the files; only users with write access to the directory can use RCS commands to change its RCS files. For example, in hosts that allow a user to belong to several groups, one can make a group's RCS directories writable to that group only. This approach suffices for informal projects, but it means that any group member can arbitrarily change the group's RCS files, and can even remove them entirely. Hence more formal projects sometimes distinguish between an RCS administrator, who can change the RCS files at will, and other project members, who can check in new revisions but cannot otherwise change the RCS files.
To prevent anybody but their RCS administrator from deleting revisions, a set of users can employ setuid privileges as follows.
seteuid
system call works as described in Posix 1003.1a Draft 5,
because RCS can switch back and forth easily
between real and effective users, even if the real user is
root.
If not, the second best is if the setuid
system call supports saved setuid
(the _POSIX_SAVED_IDS behavior of Posix 1003.1-1990);
this fails only if the real or effective user is
root.
If RCS detects any failure in setuid, it quits immediately.
A
A can invoke the rcs
command on the users' RCS files.
A should not be root
or any other user with special powers.
Mutually suspicious sets of users should use different administrators.
B to be a directory of files to
A set up B to contain copies of
ci and co that are setuid to A
by copying the commands from their standard installation directory
D as follows:
mkdir B cp D/c[io] B chmod go-w,u+s B/c[io]
B to their path as follows:
PATH=B:$PATH; export PATH # ordinary shell set path=(B $path) # C - shell
A create each RCS directory R
A
as follows:
mkdir R chmod go-w R
G,
and have A further protect the RCs directory as follows:
chgrp G R chmod g-w, o-rwx R
A copy old RCS files (if any) into
R, to ensure that A owns them.
A invoke rcs -a on the file; see rcs
In particular, rcs -e -aA limits access to just
A.
A initialize any new RCS files with
rcs -i before initial checkin, adding the
-a option if you want to limit checkin access.
ci, co,
rcsclean; do not give them to rcs
or to any other command.
RCSINIT options are prepended to the argument lists
of most RCS commands. Useful RCSINIT
options include -q, -V, -x and -z.
TMP and TEMP
are inspected instead and the first value found is taken;
if none of them are set,
a host-dependent default is used, typically
/tmp.
For each revision, ci prints the RCS file,
the working file, and the number of both the deposited and the
preceding revision. The exit status is zero if and only if all
operations were successful.
co.
co.
co and other RCS commands.
co.
co retrieves a revision from each RCS file and stores it
into the corresponding working file.
Pathnames matching an RCS suffix denote RCS files; all others denote working files. Names are paired as explained in ciIntro.
Revisions of an RCS file can be checked out locked or unlocked.
Locking a revision prevents overlapping updates. A revision
checked out for reading or processing (e.g., compiling) need not
be locked. A revision checked out for editing and later checkin
must normally be locked. Checkout with locking fails if the
revision to be checked out is currently locked by another user.
(A lock can be broken with rcs rcs). Checkout with
locking also requires the caller to be on the access list of the
RCS file, unless he is the owner of the file or the superuser,
or the access list is empty. Checkout without locking is not
subject to accesslist restrictions, and is not affected by the
presence of locks.
A revision is selected by options for revision or branch number,
checkin date/time, author, or state. When the selection options
are applied in combination, co retrieves the latest
revision that satisfies all of them. If none of the selection
options is specified, co retrieves the latest revision on
the default branch (normally the trunk, see the -b option
of rcs). A revision or branch number can be attached to any
of the options -f, -I, -l, -M,
-p, -q, -r or -u. The options
-d (date), -s(state), and -w (author)
retrieve from a single branch, the selected branch, which
is either specified by one of -f, ···, -u, or
the default branch.
A co command applied to an RCS file with no revisions
creates a zero-length working file. co always performs
keyword substitution (see below).
Overview off all options which can be given to co
Synopsis: co [options] file ···
-b option of rcs) is retrieved. If
rev is $, co determines the revision number
from keyword values in the working file. Otherwise, a revision is
composed of one or more numeric or symbolic fields separated by
periods. If rev begins with a period, then the default
branch (normally the trunk) is prepended to it. If rev is
a branch number followed by a period, then the latest revision on
that branch is used. The numeric equivalent of a symbolic field
is specified with the -n option of the commands
See ciOptn and See rcsOptn.
-r, except that it also locks the retrieved
revision for the caller.
-r, except that it unlocks the retrieved revision
if it was locked by the caller. If rev is omitted,
-u retrieves the revision locked by the caller, if there
is one; otherwise, it retrieves the latest revision on the
default branch.
-q.
See coFileModes
$Revision : 5.12 $ for the
Revision keyword. A locker's name is inserted in the value
of the Header, Id, and Locker keyword
strings only as a file is being locked, i.e. by ci -l and
co -l. This is the default.
-kkv, except that a locker's name is always inserted
if the given revision is currently locked.
Revision keyword, generate the string
$Revsion$ instead of $Revision: 5.12
$. This option is useful to ignore differences due to
keyword substitution when comparing different revisions of a
file. Log messages are inserted after $Log$ keywords
even if -kk is specified, since this tends to be more
useful when merging changes.
Revision
keyword, generate the string
$Revision: 1.1 $
instead of $Revision: 5.12 $
if that is how the string appeared when the file was checked in.
This can be useful for file formats
that cannot tolerate any changes to substrings
that happen to take the form of keyword strings.
-ko, except it performs all working file input and output
in binary mode. This makes little difference on Posix and Unix
hosts, but on DOS-like hosts one should use rcs -i -kb to
initialize an RCS file intended to be used for binary files.
Also, on all hosts, rcsmerge normally refuses to merge
files when -kb is in effect.
Revision keyword, generate the string 5.12
instead of $Revision: 5.12 $
This can help generate files in programming languages where it
is hard to strip keyword delimiters like
$Revision: $ from a string.
However, further keyword substitution cannot be performed once
the keyword names are removed, so this option should be used
with care. Because of this danger of losing keywords, this
option cannot be combined with -l, and the owner write
permission of the working file is turned off; to edit
the file later, check it out again without -kv.
co is part of a pipe.
LT stands for local time;
other common time zone names are understood.
For example, the following
dates are equivalent
if local time is January 11, 1990, 8pm Pacific Standard Time,
eight hours west of Coordinated Universal Time (UTC):
8:00 pm lt 4:00 AM, Jan. 12, 1990 default is UTC 1990-01-12 04:00:00+00 ISO 8601 (UTC) 1990-01-11 20:00:00-08 ISO 8601 (local time) 1990/01/12 04:00:00 traditional RCS format Thu Jan 11 20:00:00 1990 LT output of ctime(3) + LT Thu Jan 11 20:00:00 PST 1990 output of date(1) Fri Jan 12 04:00:00 GMT 1990 Thu, 11 Jan 1990 20:00:00 -0800 Internet RFC 822 12-January-1990, 04:00 WET
Most fields in the date and time can be defaulted. The default
time zone is normally UTC, but this can be overridden by the
-z option. The other defaults are determined in the order
year, month, day, hour, minute, and second (most to least
significant). At least one of these fields must be provided.
For omitted fields that are of higher significance than the
highest provided field, the time zone's current values are
assumed. For all other omitted fields, the lowest possible values
are assumed. For example, without -z, the date 20,
10:30 defaults to 10:30:00 UTC of the 20th of the UTC time
zone's current month and year. The date/time must be quoted if it
contains spaces.
make.
make
dependency of some other copy of the working file on the RCS
file. Use this option with care; it can suppress recompilation
even when it is needed, i.e. when the change of lock would mean a
change to keyword strings in the other working file.
rcsmerge
(rcsmerge) but is retained for backwards compatibility.
The joinlist is a comma-separated list of pairs of the
form rev2 : rev3, where rev2 and rev3 are
(symbolic or numeric) revision numbers. For the initial such
pair, rev1 denotes the revision selected by the above
options -f, ···, -w. For all other pairs,
rev1 denotes the revision generated by the previous pair.
(Thus, the output of one join becomes the input to the next.)
For each pair, co joins revisions rev1 and
rev3 with respect to rev2. This means that all
changes that transform rev2 into rev1 are applied
to a copy of rev3. This is particularly useful if
rev1 and rev3 are the ends of two branches that
have rev2 as a common ancestor. If
rev1 < rev2 < rev3 on the same branch,
joining generates a new revision which is like rev3,
but with all changes that lead from rev1 to rev2
undone. If changes from rev2 to rev1 overlap
with changes from rev2 to rev3, co reports
overlaps as described in merge.
For the initial pair, rev2 can be omitted. The default is
the common ancestor. If any of the arguments indicate branches,
the latest revisions on those branches are assumed. The options
-l and -u lock or unlock rev1.
3,
4, or 5. This can be useful when interchanging RCS
files with others who are running older versions of RCS. To see
which version of RCS your correspondents are running, have them
invoke rcs -V; this works with newer versions of RCS. If
it doesn't work, have them invoke rlog (rlog) on an
RCS file; if none of the first few lines of output contain the
string branch: it is version 3; if the dates' years have
just two digits, it is version 4; otherwise, it is version 5. An
RCS file generated while emulating version 3 loses its default
branch. An RCS revision generated while emulating version 4 or
earlier has a time stamp that is off by up to 13 hours. A
revision extracted while emulating version 4 or earlier contains
abbreviated dates of the form yy/mm/dd and can also
contain different white space and line prefixes in the
substitution for $Log$.
$keyword$ and
$keyword : ···$ embedded in
the text are replaced with strings of the form
$keyword:value$ where
keyword and value are pairs listed below.
Keywords can be embedded in literal strings or comments to
identify a revision.
Initially, the user enters strings of the form
$keyword$.
On checkout, co replaces these strings with strings
of the form $keyword:value$.
If a revision containing strings of the latter form is checked
back in, the value fields will be replaced during the next
checkout. Thus, the keyword values are automatically updated on
checkout. This automatic substitution can be modified by the
-k options.
Keywords and their corresponding values:
-zzone a numeric time zone offset is appended;
otherwise, the date is UTC.
-zzone
a numeric time zone offset is appended to the date;
otherwise, the date is RCS.
$Header$,
except that the RCS filename is without a path.
-zzone a numeric time zone
offset is appended; otherwise, the date is UTC. Existing log
messages are not replaced. Instead, the new log message is
inserted after $Log: ··· $. This
is useful for accumulating a complete change log in a source
file.
Each inserted line is prefixed by the string that prefixes the
$Log$ line. For example, if the
$Log$ line is
"// $Log: tan.cc $",
RCS prefixes each line of the log with "// ".
This is useful for languages with comments that go to the
end of the line. The convention for other languages is to use a
" * " prefix inside a multiline comment. For example,
the initial log comment of a C program conventionally is of
the following form:
/* * $Log$ */
For backwards compatibility with older versions of RCS, if the
log prefix is /* or (* surrounded by optional
white space, inserted log lines contain a space instead of
/ or (; however, this usage is obsolescent and
should not be relied on.
"co -rJoe" generates
"$Name: Joe $".
Plain co generates just "$Name: $"
-s option of rcs or ci.
The following characters in keyword values are represented by escape sequences to keep keyword strings well-formed.
charescape sequencetab \t newline \n space \040 $ \044 \ \\
-kv is set or the file is checked
out unlocked and locking is set to strict (See rcs).
If a file with the name of the working file exists already and
has write permission, co aborts the checkout, asking
beforehand if possible. If the existing working file is not
writable or -f is given, the working file is deleted
without asking.
co accesses files much as ci does, except that it
does not need to read the working file unless a revision number
of $ is specified.
rcs.
rcs.
rcs.
RCS creates new RCS files or changes attributes of existing ones.
An RCS file contains multiple revisions of
text, an access list, a change log, descriptive text, and
some control attributes. For rcs to work, the caller's
login name must be on the access list, except if the
access list is empty, the caller is the owner of the file
or the superuser, or the -i option is present.
Pathnames matching an RCS suffix denote RCS files; all others denote working files. Names are paired as explained in See ciIntro. Revision numbers use the syntax described in See ciIntro.
Overview off all options which can be given to rcs
Synopsis: rcs [options] file ···
./RCS, and then into the current directory. If the
RCS file already exists, print an error message.
ci, or an rcs -i without -c,
guesses the comment leader from the suffix of the
working filename.
This option is obsolescent, since RCS normally uses
the preceding $Log$ line's prefix
when inserting log lines during checkout
(See coIntro).
However, older versions of RCS use the comment leader
instead of the $Log$ line's prefix,
so if you plan to access a file with both old and
new versions of RCS, make sure its comment leader
matches its $Log$ line prefix.
-k option to co,
rcsdiff, and rcsmerge overrides this default.
Beware rcs -kv, because -kv is incompatible with
co -l. Use rcs -kkv to restore the normal default keyword
substitution.
rcs -u (see below).
. by itself.
strict. Strict locking means that
the owner of an RCS file is not exempt from locking
for checkin. This option should be used for files
that are shared.
not be
used for files that are shared. Whether default
locking is strict is determined by your system
administrator, but it is normally strict.
rcs -u only as a low-level
lock-breaking operation.
rcs -nname: RCS/*
associates name with the current
latest revision of all the named RCS files; this
contrasts with
rcs -nname:$ RCS/*
which associates
name with the revision numbers extracted from keyword
strings in the corresponding working files.
-n, except override any previous assignment of
name.
rev1:rev2 means
revisions rev1 to rev2 on the same branch,
:rev means from the beginning of the branch
containing rev up to and including rev,
and rev: means from revision rev to the
end of the branch containing rev . None of the
outdated revisions can have branches or locks.
-.
If file is omitted, obtain the text from standard
input, terminated by end-of-file or by a line containing.
by itself. Prompt for the text if interaction is possible;
see -I rcsOptIu. With -i, descriptive
text is obtained even if -t is not given.
make
dependency of some copy of the working file on the
RCS file. Use this option with care; it can suppress
recompilation even when it is needed, i.e.
when a change to the RCS file would mean a change
to keyword strings in the working file.
-brev option generates an RCS file that cannot be
parsed by RCS version 3 or earlier.
The -ksubst options (except -kkv) generate an RCS file
that cannot be parsed by RCS version 4 or earlier.
Use rcs -Vn to make an RCS file acceptable to RCS version
n by discarding information that would confuse version n.
RCS version 5.5 and earlier does not support the -x
option, and requires a ,v suffix on an RCS pathname.
rcs accesses files much as ci does, except that it uses
the effective user for all accesses, it does not write the
working file or its directory, and it does not even read
The separator for revision ranges in the -o option used to
be - instead of :, but this leads to confusion when
symbolic names contain -. For backwards compatibility
rcs -o still supports the old - separator, but it warns about
this obsolete use.
Symbolic names need not refer to existing revisions or
branches. For example, the -o option does not remove symbolic
names for the outdated revisions; you must use -n to
remove the names.
Ident searches for all instances of the pattern
$keyword: text $ in the named
files or, if no files are named, the standard input.
These patterns are normally inserted automatically by the
RCS command co (coKeyword), but can also
be inserted manually. The option
-q(See identOptq) suppresses the
warning given if there are no patterns in a file.
The option -V(See identOptV) prints ident's version
number.
ident works on text files as well as object files and dumps. For example, if the C program in f.c contains:
#include <stdio.h>
static char const rcsid[] =
"$Id: f.c,v 5.4 1993/11/09 17:40:15 eggert Exp $";
int main() { return printf("%s\n", rcsid) == EOF; }
and f.c is compiled into f.o, then the command
ident f.c f.o
will output
f.c:
$Id: f.c,v 5.4 1993/11/09 17:40:15 eggert Exp $
f.o:
$Id: f.c,v 5.4 1993/11/09 17:40:15 eggert Exp $
If a C program defines a string like rcsid above but does
not use it, lint may complain, and some C compilers
will optimize away the string. The most reliable solution
is to have the program use the rcsid string, as shown in
the example above.
ident finds all instances of the $keyword: text $
pattern, even if keyword is not actually an RCS-supported keyword.
This gives you information about nonstandard keywords like
$XConsortium$.
Overview off all options which can be given to rcs
Synopsis: ident [options] [ file ··· ]
co you'll find
in coKeyword.
co's -zzone (See coOptz)
option, times are given with a numeric time zone indication appended.
rcsclean.
rcsclean.
rcsclean.
rcsclean.
rcsclean removes files that are not being worked on.
rcsclean -u (rcscleanOptu) also unlocks and removes
files that are being worked on but have not changed.
For each file given, rcsclean compares the working file
and a revision in the corresponding RCS file. If it finds
a difference, it does nothing. Otherwise, it first
unlocks the revision if the -u (See rcscleanOptu
option is given, and then
removes the working file unless the working file is
writable and the revision is locked. It logs its actions
by outputting the corresponding rcs -u (See rcsOptu)
and rm -f commands on the standard output.
Files are paired as explained in ciFiles. If no file is given, all working files in the current directory are cleaned. Pathnames matching an RCS suffix denote RCS files; all others denote working files.
The number of the revision to which the working file is
compared may be attached to any of the options -n,
-q, -r, or -u.
If no revision number is specified, then if the -u
option is given and the caller has one revision locked,
rcsclean uses that revision; otherwise rcsclean uses the
latest revision on the default branch, normally the root.
rcsclean is useful for clean targets in makefiles.
See rcsdiff, which prints out the differences, and
ci (ciIntro), which normally reverts to the
previous revision if a file was not changed.
Overview off all options which can be given to rcsclean
Synopsis: rcsclean [options] [ file ··· ]
rcsclean would do without actually doing it.
make dependency of some other copy
of the working file on the RCS file. Use this
option with care; it can suppress recompilation
even when it is needed, i.e. when the lock removal
would mean a change to keyword strings in the other
working file.
-zzone Use zone as the time zone for keyword substitution;
see coOptz for details.
rcsclean *.c *.h
removes all working files ending in .c or .h that were not changed since their checkout.
rcsclean
removes all working files in the current directory that were not changed since their checkout.
rcsclean accesses files much as ci (ciFiles)does.
rcsdiff.
rcsdiff.
rcsdiff.
rcsdiff.
rcsdiff runs diff to compare two revisions of each RCS
file given.
Pathnames matching an RCS suffix denote RCS files; all others denote working files. Names are paired as explained in ciFiles.
Overview off all options which can be given to rcsdiff
Synopsis: rcsdiff [options] [-rrev1] [-rrev2] [diff options] [ file ··· ]
-ksubst affects keyword substitution when extracting
revisions, as described in coOptk; for example,
-kk -r1.1 -r1.2 ignores differences in keyword values
when comparing revisions 1.1 and 1.2.
To avoid excess output from locker name substitution,
-kkvl is assumed if
-k option is given,
-kkv is the default keyword substitution, and
co -l.
-r.
If both rev1 and rev2 are omitted, rcsdiff compares the
latest revision on the default branch (by default the
trunk) with the contents of the corresponding working
file. This is useful for determining what you changed
since the last checkin.
If rev1 is given, but rev2 is omitted, rcsdiff compares revision rev1 of the RCS file with the contents of the corresponding working file.
If both rev1 and rev2 are given, rcsdiff compares revisions rev1 and rev2 of the RCS file.
Both rev1 and rev2 may be given numerically or symbolically.
rcsdiff *.c *.h
removes all working files ending in .c or .h that were not changed since their checkout.
rcsdiff
removes all working files in the current directory that were not changed since their checkout.
rcs.
rcs.
rcsmerge.
rcs.
rcsmerge incorporates the changes between two revisions of an RCS file into the corresponding working file.
Pathnames matching an RCS suffix denote RCS files; all others denote working files. Names are paired as explained in ciFiles.
At least one revision must be specified with one of the
options described below, usually -r.
At most two revisions may be specified. If only one
revision is specified, the latest revision on the
default branch (normally the highest branch on the
trunk) is assumed for the second revision.
Revisions may be specified numerically or symbolically.
rcsmerge prints a warning if there are overlaps, and delimits the overlapping regions as explained in merge. The command is useful for incorporating changes into a checked-out revision.
Overview off all options which can be given to rcsmerge
Synopsis: rcsmerge [options] file ···
-A style of diff3, if
supported by diff3. This merges all changes leading
from file2 to file3 into file1, and generates
the most verbose output.
-A. See diff3 for
details. The default is -E. With -e, rcsmerge
does not warn about conflicts.
-kk -r1.1 -r1.2 ignores
differences in keyword values when merging the
changes from 1.1 to 1.2. It normally
does not make sense to merge binary files as if
they were text, so rcsmerge refuses to merge
files if -kb expansion is used.
2.8 of f.c. Assume
furthermore that after you complete an unreleased revision
3.4, you receive updates to release 2.8 from someone else.
To combine the updates to 2.8 and your changes between 2.8
and 3.4, put the updates to 2.8 into file f.c and execute
rcsmerge -p -r2.8 -r3.4 f.c >f.merged.c
Then examine f.merged.c. Alternatively, if you want to
save the updates to 2.8 in the RCS file, check them in as
revision 2.8.1.1 and execute co -j:
ci -r2.8.1.1 f.c co -r3.4 -j2.8:2.8.1.1 f.c
As another example, the following command undoes the
changes between revision 2.4 and 2.8 in your currently
checked out revision in f.c.
rcsmerge -r2.8 -r2.4 f.c
Note the order of the arguments, and that f.c will be overwritten.
rlog.
rlog.
rlog.
rlog prints information about RCS files.
Pathnames matching an RCS suffix denote RCS files; all others denote working files. Names are paired as explained in ciFiles.
rlog prints the following information for each RCS file:
RCS pathname, working pathname, head (i.e., the number of
the latest revision on the trunk), default branch, access
list, locks, symbolic names, suffix, total number of revisions,
number of revisions selected for printing, and
descriptive text. This is followed by entries for the
selected revisions in reverse chronological order for each
branch. For each revision, rlog prints revision number,
author, date/time, state, number of lines added/deleted
(with respect to the previous revision), locker of the
revision (if any), and log message. All times are displayed
in Coordinated Universal Time (UTC) by default;
this can be overridden with -z. Without options,
rlog prints complete information.
The options below restrict this output.
Overview off all options which can be given to rlog
Synopsis: rlog [options] file ···
-h, -l, and -R.
-h, plus the descriptive text.
< or
> is followed by = then the ranges are inclusive,
not exclusive. A range of the form d selects the
single, latest revision dated d or earlier. The date/time
strings d, d1, and d2 are in the free
format explained in coOptd. Quoting is normally necessary,
especially for < and >. Note that the separator is
a semicolon.
rlog -L -R -lwft RCS/*
prints the name of RCS files locked by the user wft.
revisions of revisions and ranges. A range
rev1:rev2 means revisions rev1 to
rev2 on the same branch, :rev means
revisions from the beginning of the branch up to and including
rev , and rev: means revisions starting
with rev to the end of the branch containing rev.
An argument that is a branch means all revisions on that branch.
A range of branches means all revisions on the branches in
that range. A branch followed by a . means the latest revision
in that branch. A bare -r with no revisions means
the latest revision on the default branch, normally the trunk.
-d, -l, -s, and -w,
intersected with the union of the revisions selected by
-b and -r.
-ddates option.
The zone should be empty, a numeric UTC offset, or
the special string LT for local time. The default
is an empty zone , which uses the traditional RCS
format of UTC without any time zone indication and
with slashes separating the parts of the date; oth-
erwise, times are output in ISO 8601 format with
time zone indication. For example, if local time
is January 11, 1990, 8pm Pacific Standard Time,
eight hours west of UTC, then the time is output as
follows:
option time output -z 1990/01/12 04:00:00 (default) -zLT 1990-01-11 20:00:00-08 -z+05:30 1990-01-12 09:30:00+05:30
rlog -L -R RCS/* rlog -L -h RCS/* rlog -L -l RCS/* rlog RCS/*
The first command prints the names of all RCS files in the subdirectory RCS that have locks. The second command prints the headers of those files, and the third prints the headers plus the log messages of the locked revisions. The last command prints complete information.
-r option used to
be - instead of :, but this leads to confusion when symbolic
names contain -. For backwards compatibility
rlog -r still supports the old - separator, but it warns about
this obsolete use.
merge incorporates all changes that lead from file2 to
file3 into file1. The result ordinarily goes
into file1.
merge is useful for combining separate changes to an original.
Suppose file2 is the original, and both file1 and
file3 are modifications of file2 . Then merge combines
both changes.
A conflict occurs if both file1 and file3 have changes in
a common segment of lines. If a conflict is found, merge
normally outputs a warning and brackets the conflict with
<<<<<<< and >>>>>>> lines. A typical conflict will look
like this:
<<<<<<< file A lines in file A ======= lines in file B >>>>>>> file B
If there are conflicts, the user should edit the result and delete one of the alternatives.
merge
Synopsis: merge [options] file1 file2 file3
-A style of diff3, if
supported by diff3. This merges all changes leading
from file2 to file3 into file1, and generates
the most verbose output.
-A. See diff3 for
details. The default is -E. With -e, merge does
not warn about conflicts.
merge -L x -L y -L z a b c generates output that
looks like it came from files x, y and zinstead of
from files a, b and c.
An RCS file's contents are described by the grammar below.
The text is free format: space, backspace, tab, newline,
vertical tab, form feed, and carriage return (collectively,
white space) have no significance except in
strings. However, white space cannot appear within an id,
num, or sym, and an RCS file must end with a newline.
Strings are enclosed by @. If a string contains a @, it must be doubled; otherwise, strings can contain arbitrary binary data.
The meta syntax uses the following conventions: `|' (bar)
separates alternatives; `{' and `}' enclose optional
phrases; `{' and `}*' enclose phrases that can be repeated
zero or more times; `{' and '}+' enclose phrases that must
appear at least once and can be repeated; Terminal symbols
are in boldface; nonterminal symbols are in italic.
rcstext ::= admin {delta}* desc {deltatext}*
admin ::= head {num};
{ branch {num}; }
access {id}*;
symbols {sym : num}*;
locks {id : num}*; {strict ;}
{ comment {string}; }
{ expand {string}; }
{ newphrase }*
delta ::= num
date num;
author id;
state {id};
branches {num}*;
next {num};
{ newphrase }*
desc ::= desc string
deltatext ::= num
log string
{ newphrase }*
text string
num ::= {digit | .}+
digit ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
id ::= {num} idchar {idchar | num }*
sym ::= {digit}* idchar {idchar | digit }*
idchar ::= any visible graphic character except special
special ::= $ | , | . | : | ; | @
string ::= @{any character, with @ doubled}*@
newphrase ::= id word* ;
word ::= id | num | string | :
Identifiers are case sensitive. Keywords are in lower case only. The sets of keywords and identifiers can overlap. In most environments RCS uses the ISO 8859/1 encoding: visible graphic characters are codes 041-176 and 240-377, and white space characters are codes 010-015 and 040.
Dates, which appear after the date keyword, are of the form
Y.mm.dd.hh.mm.ss, where Y is the year, mm
the month (01-12), dd the day (01-31), hh the hour
(00-23), mm the minute (00-59), and ss the
second (00-60). Y contains just the last two digits of the
year for years from 1900 through 1999, and all the digits
of years thereafter. Dates use the Gregorian calendar; times use
UTC.
The newphrase productions in the grammar are reserved
for future extensions to the format of RCS files. No
newphrase will begin with any keyword already in use.
The delta nodes form a tree. All nodes whose numbers consist
of a single pair (e.g., 2.3, 2.1, 1.3, etc.) are on
the trunk, and are linked through the next field in order
of decreasing numbers. The head field in the admin node
points to the head of that sequence (i.e., contains the
highest pair). The branch node in the admin node indicates
the default branch (or revision) for most RCS operations.
If empty, the default branch is the highest branch
on the trunk.
All delta nodes whose numbers consist of 2n fields
(n>=2) (e.g., 3.1.1.1, 2.1.2.2, etc.) are linked as follows.
All nodes whose first 2n-1 number fields are identical are
linked through the next field in order of increasing numbers.
For each such sequence, the delta node whose number
is identical to the first 2n-2 number fields of the deltas
on that sequence is called the branchpoint. The branches
field of a node contains a list of the numbers of the
first nodes of all sequences for which it is a branchpoint.
This list is ordered in increasing numbers.
Head
|
v / \
--------- / \
/ \ / \ | | / \ / \
/ \ / \ | 2.1 | / \ / \
/ \ / \ | | / \ / \
/1.2.1.3\ /1.3.1.1\ | | /1.2.2.2\ /1.2.2.1.1.1\
--------- --------- --------- --------- -------------
^ ^ | ^ ^
| | v | |
/ \ | --------- / \ |
/ \ | \ 1.3 / / \ |
/ \ ---------\ / / \-----------
/1.2.1.1\ \ / /1.2.2.1\
--------- \ / ---------
^ | ^
| v |
| --------- |
| \ 1.2 / |
----------------------\ /---------
\ /
\ /
|
v
---------
\ 1.1 /
\ /
\ /
\ /
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