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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
NAME NAME
pc-shell - pc command processor
SYNOPSIS SYNOPSIS
pc shell pc-shell [-s] [-v] [arg1 ... argn]
DESCRIPTION DESCRIPTION
pc-shell is a command processor for IBM-PC's and compatibles that
emulates some of the more desirable functions of the Berkeley
UNIX* C-shell. In addition, it implements PC-DOS versions of some
of the common UNIX* commands - ls, mv, cp, etc.
s The -s option causes the program execute a file called "shell.rc"
in the current directory before passing control to the user. If
"shell.rc" is not found in the current directory, the directory
specified by the environment string "HOME" will be searched.
v The -v option (verbose) causes the program to echo all commands
to the standard error stream before executing them.
arg1 argn arg1 ... argn (the command line arguments) are put into the
shell's environment as the variables $1 through $n.
Wild Card Substitution Wild Card Substitution
Ambiguous file names are expanded to a list of matching file
names on the command line. This can be defeated by quoting, and
by setting the NOGLOB environment variable to '1'.
Command lines passed to external programs are truncated to 128
characters.
History Substitution History Substitution
History substitution is a powerful means to save retyping of long
command lines.It allows you to do things like re-execute the last
command, re-execute the last command but redirect output to a
file, or execute a new command with arguments from previous
command lines. The last 20 commands are saved, and can be
reviewed by typing the 'history' command.
Previous commands can be referred to by their number, or relative
to the current command's number. Parameters from previous
commands can be seperated out and used individually.
History substitutions specifications come in two parts - the
command number specifier and the argument specifier, seperated
by a colon. The argument specifier is optional; if it is
omitted, the entire command line is specified.
<command specifier> ::= !! | !n | !-n
!! = last command
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
!n = nth command
!-n = command n commands before current command number
!# = the current command line
<arg specifier> ::= :[^$*] | :n | :n* | <empty>
n = number of argument (0 being the command name)
^ = first argument (i.e. argv[1])
$ = last argument
* = ^-$, or nothing if only one word on command line
n* = arguments n through $
<history subst specification> ::= <command specifier><arg specifier>
This is not as complicatated as it may appear. Here is an
example session.
EXAMPLE
0% ls *.c
*.c
foo.c bar.c
1% more foo.c
/* edit the last argument of the last command */
2% edit !!:$
/* go off and edit */
/* reference last argument of last command */
3% fgrep foo !!:$ bar.c
FOO.C : foo
BAR.C : foo
/* edit the second thru the last args of command 3 */
4% edit !3:2*
(go off and edit)
/* repeat last command */
%5 !!
(go off and edit)
/* remove the 1st argument of the command 2 before the current one */
%6 rm !-6:^
History substitution here is a compatible subset of the [U|XE]NIX
C shell history substitution facility. Cshell allows even
weirder combinations.
Variable Substitution Variable Substitution
Shell variables are synonymous for our purposes with environment
strings, i.e. they are defined with the 'set' command.
Variables are referenced on the command line by prefacing a
variable name by a dollar sign. Two dollar signs in a row
signify a dollar sign character.
As mentioned above, command line arguments are contained in the
n shell variables, $1 through $n, where n is the number of the last
argument.
EXAMPLE
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
%0 set home = c:/
%1 echo $home
C:/
%2 ls $home
C:/*.*
command.com
%3 echo $path
C:/bin
And so on.
Special variables Special variables
There are a some shell variables that have special meanings for
set the shell. They can be given values with the set command. They
are
NOCLOBBER NOCLOBBER
NOCLOBBER If NOCLOBBER is equal to '1', then existing files may not be
destroyed by output redirection, and output files to be
appended to by >> must exist.
PROMPT PROMPT
PROMPT The PROMPT environment string is handled the same way as it
COMMAND COM is by COMMAND.COM. There is one pc-shell-specific prompt
string character ! that specifies the current command
index. If no PROMPT environment string is defined, then the
default is '$!% '.
NOGLOB NOGLOB
NOGLOB The NOGLOB environment string, if set to '1', will suppress file
name expansion.
Multiple commands on one command line Multiple commands on one command line
Command lines are split at semicolons. This can be defeated by
quoting or escaping.
EXAMPLE
%0 ls -l *.c ; make shell.exe ; exit
Conditional command execution Conditional command execution
If two commands are seperated by '&&', then the second will be
executed only if the first returns 0 as an exit code. If two
commands are seperated by '||', then the second will be executed
only the first command returns non-zero as an exit code.
Example
make shell.exe && chmod +w /bin/shell.exe && mv shell.exe /bin
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
If the make operation fails, then the chmod and the mv will
not be executed.
make shell.exe || echo You blew it bub!
If the make operation fails, then the echo operation will be
executed.
Character Escapes Shell Comments and Argument Quoting Character Escapes, Shell Comments, and Argument Quoting
Any character preceded by a \ (backslash) is copied unmodified
to the command buffer. This allows you to suppress the special
meanings of shell command characters, such as '|', ';', and '*
'.
# is the shell comment character. Anything on a line after a #
character is ignored.
Command line arguments contained in quotes (single or double) may
contain blank space (i.e. blanks or tabs). Variable substitution
will take place within strings surrounded by double quotes. No
interpretation takes place within single quotes.
Within double quotes, the 'C' language escape sequences
\r,\n,\b,\f, and \a are honored - i.e. they are mapped to their
corresponding control characters.
Startup and Script Files Startup and Script Files
If '-s' is specified on the command line the program will look
for a file called SHELL.RC in the current directory, and execute
it before passing control to the console. This allows you to
set up all your alias commands. It isn't a good idea to put an
'exit' command in your SHELL.RC file, as the shell will
terminate.
sh Any file whose extension is .sh is run as a command file. The
environment string PATH is used to locate the script file if it
isn't in the current directory. .sp 1 There is also a command
sh sh, into which shell scripts whose extension is not .sh can be
redirected as standard input.
EXAMPLE
%0 sh <batch.fil # use the sh command
%1 shell <batch.fil # run the external program
INPUT OUTPUT INPUT/OUTPUT
COMMAND COM I/O redirection operates as it does under COMMAND.COM with some
additional options:
name <name
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
name Opens the file name as the standard input.
word <<word
word reads the shell input up to a line which is identical to word.
The resulting text is put into an anonymous temporary file, which
is given to the command as standard input.
name >name
name >!name
name >&name
name >&!name
name The file name is used as standard output. If it doesn't
exist, it's created; if it exists, it is truncated, and its
previous contents are lost.
NOCLOBBER If the variable NOCLOBBER is set, the file must not already
exist, or an error results. The forms using an exclamation
point override the NOCLOBBER variable's action.
name The form >&name routes standard error along with standard
name output to name.
name >>name
name >>!name
name >>&name
name >>&!name
name Uses the file name as standard output, like >, but places
NOCLOBBER output at the end of file. If the variable NOCLOBBER is set,
it is an error if the file doesn't already exist. The forms
using an exclamation point override the NOCLOBBER variable's
action.
BUILT IN COMMANDS BUILT-IN COMMANDS
Some of the internal commands are UNIX* style replacements
for COMMAND.COM internal commands, and some are included for
convenience.
Output of the 'commands' command
a: alias b: c:
cat cd chdir chmod
cls commands copy cp
d: del dir dump
e: echo era erase
error exit f: fgrep
g: h: hd history
i: j: ls md
mkdir mon more mv
popd pushd pwd rd
read rm rmdir set
sh switchar tee touch
unalias version y
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
There are many that are simply aliases, e.g. 'copy' and 'cp'
invoke the same program.
COMMAND DESCRIPTION SYNTAX COMMAND DESCRIPTION SYNTAX
terms used in syntax explanations :
fname ::= PC-DOS ambiguous or unambiguous file or directory name.
uname ::= unambiguous PC-DOS file or directory name
string ::= any string of printable characters of arbitrary(<512) length.
filelist ::= filename [filename .. filename]
noargs ::= no arguments at all
space ::= any white space characters
[arg] ::= term is optional
envstring ::= <string>=<string> | <string><space>=<space><string> |
<string><space><string>
COMMANDS COMMANDS
drive drive
a: | b: | c: | d: | e: | f: | g: | h: | i: | j: <noargs>
changes default drive. If you don't have such a drive,
nothing happens.
alias alias
alias <envstring>
assigns cmdstring to name. name can now be used just as
if it were a built-in or external command. cmdstring may
contain history expressions or variable substitutions.
The syntax of this command is flexible - you can specify
alii (?) in the form 'name=subst','name subst','name =
subst', or 'name =subst.' However you need a space
before character before a single quote in order to specify an
alias that contains blanks.
alias set The alias and set commands are case sensitive, unlike
COMMAND COM their analogs in COMMAND.COM.
cat cat
cat [<filelist>]
copies specified files to standard output. If none are
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
given, copies standard input to standard output
cp cp
cp | copy <filelist> <uname>
copies specified files to destination file or device. If
more than one file is in the file list, <uname> must be a
directory.
cd cd
cd | chdir <dirname>
makes <dirname> the current default directory.
chmod chmod
chmod [-|+[arwhs]*] <filelist>
change file permissions for specified files
+r, -r turn on or off read permission - i.e. hide the file.
+w, -w turn on or off write permission.
+h, -h turn on or off hidden attribute - converse of r
+a, -a turn on or off archive attribute
+s, -s turns on or off the system attribute
Note that '-r' or '+rwh' are both valid syntax for
switches. Also new permission switches are permissable
between file names with the following warning: I don't
reset the masks between file names - if you have a second
batch of attribute changes on the command line, the
effect is additive. If you're not careful, you could
make a mess of a files attributes.
If you don't specify any attribute switches, file
attributes will be set to 0, which means read,write,not
hidden,not system, not modified since last backup.
cls cls
cls <noargs>
clears the screen and homes the cursor.
commands commands
commands <noargs>
prints a table of available built-in commands. (see
above)
del del
del
synonym for rm.
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
dir dir
dir
synonym for ls.
dirs dirs
dirs <noargs>
lists the directories on the directory stack. (see pushd
and popd)
du du
du [drivename]
drivename prints out remaining space on drive drivename. If you
leave off the drivename, it defaults to the current
drive.
dump dump
dump filespec [block [page]] | [segment:[offset]] [count]
Where a block is 64K bytes and a page is 256 bytes
Segment:offset are standard 8086 notation in hexadecimal
Count is the number of bytes to dump in decimal
This came from some anonymous public domain source, ported by me
echo echo
echo <anything>
echo on echos argument list to screen. echo on causes all
commands to be echoed before execution (i.e. sets the
echo off verbose flag). echo off turns off the verbose flag.
era era
era
synonym for rm.
error error
error <noargs>
prints returned value of last command to the screen.
exit exit
exit <noargs>
terminates execution of the currently running sub-shell.
If you are at top level of execution, you will return to
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
dos.
fgrep fgrep
fgrep <pattern> <filelist>
looks for unambiguous pattern <pattern> in <filelist>.
echos lines matching to the screen.
history history
history [size]
size prints history list to standard output. If size is
given, the number of commands history remembers is set to
size size. If you change the size, history 'forgets' all
previous commands and resets its counters to 0.
ls ls
ls | dir [-[alqctrR]] <filelist>
Lists files that match <filelist>
-a all files, including system files are listed. '.' and
'..' are suppressed, but you know they're there if you
need them, don't you?
-l prints out file times, permissions, etc
-q suppresses header line from display - useful when you
want to pipe stuff into another program.
-c print as one column.
-t sort by time, most recent last
-R recurse through all encountered subdirectories.
-r reverses sort order.
md md
md | mkdir <uname>
make a directory. Prints an error if it can't be done
mon mon
mon <noargs>
mon mon prints to standard error a lot of cryptic information
on system variables thusly:
Corg : 0000 Cend : 715a Dorg : 0002 Dend 167a
Uorg : 167a Uend : 327a mbot : 427c mtop 4800
sbot : 0000 PSP : 490d STKSIZ : 00256 HEAPSIZ : 00064
dsval : 5033 csval : 491d
STKLOW : 0001 MEMRY : 4680
CS : 491d DS : 5033 SP : 4186
You can probably figure out what most of the variables
mean. If you have source and have broken the shell, this
command may help.
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
more more
more [-[0-9]*] [<filelist>]
List file to screen with pauses
-n specify tab width when expanding tabs, where n is an
integer. more acts like 'cat' when redirected - you can
concatenate files in this manner. If no files are
specifed, standard input is 'mored.'
mv mv
mv [-v] <filelist> <uname>
moves specified file or files to target specifed by
<uname>. If there is more than one file in list, <uname>
must be a directory
v -v will print out a message saying how it is
accomplishing the move, which is probably more
interesting to me than you.
popd popd
popd <noargs>
returns to directory at top of directory stack.
pushd pushd
pushd <uname>
save current working directory on directory stack, and
changes current working directory to <uname>.
pwd pwd
pwd
prints current working directory to standard output.
read read
read vname0 [vname1 .. vnamen]
read read reads a line from standard input, and assigns each
word from the line to the corresponding environment
vname0 vnamen variable specified by vname0 through vnamen.
EXAMPLE
read a b # read into environment variables a and b
you type
hello there
echo $a
the shell echos
hello
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
echo $b
there
If there are fewer environment variables specified on the
command line than there are words in the command line,
the last environment variable will contain the rest of
the words on the line.
EXAMPLE
read a b # read into environment variables a and b
you type
hello there Mister Jones
echo $a
the shell echos
hello
echo $b
there Mister Jones
If there are more environment variables on the command
line than words on the line read from standard input, the
left-over environment variables' state will not change -
if they were defined in the environment already, their
status won't change, and if they weren't defined, they
stay undefined.
rd rd
rd | rmdir <uname>
remove specified directory if possible.
rm rm
rm [-q] <filelist>
blows away all files in <filelist>. If -q is specified,
will ask if they should be removed.
set set
set [<envstring>]
sets a string in the environment. If you specify 'name='
with no string after, it will remove it from the
environment. If you don't specify a string, set prints
out current environment.
The syntax of this command is flexible - you can specify
set in the form 'set name=subst','set name subst','set
name = subst', or 'set name =subst.' However you need a
before space character before a single quote in order to specify
a substitution string that contains blanks.
sh sh
sh [ <arg1> .. <argn>] <scriptfile
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
forks a 'local' shell - i.e. saves all pertinent
information about the shell you're currently in and
invokes the command processor function recursively, with
scriptfile scriptfile as input. The arguments are copied to $1
through $N environment strings, overwriting the startup
arguments.
sh sh gives you a way to run scripts, without loading an
extra copy of shell.com or small.com.
switchar switchar
switchar [schar]
schar schar sets the DOS switch character to schar. If schar is not
given, the current switch character is echoed.
tee tee
tee <uname>
Copies standard input to standard output, depositing a
copy in <uname>
touch touch
touch <filelist>
Makes the modification time of specified files the
current date and time.
unalias unalias
unalias aliasname
remove alias name from the alias list.
y y
y <filelist>
copies standard input to standard output, and then copies
the specified files to standard output. Sort of the
opposite of tee, in other words.
The Small Shell The Small Shell
Included in release 2.0 or later is a 'small' version of the
shell. This version will take up less than 30K of memory at
runtime (as verified by chkdsk). What's the catch? Well,
ls, cp, mv, more, fgrep, and dump become external commands.
I am not going to distribute these commands; you can either
make them yourself, or you can use whatever you have on
hand. If you need to use the COMMAND.COM copy facility, try
putting these commands in your SHELL.RC file
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
alias cp 'command -c copy'
alias ls 'command -c dir -w | sort'
The removed commands accounted for over 10K of the
shell.com.
Helpful hints Helpful hints
Use forward slashes in all path names. (See note below on
switch characters) If you use DOS 3.0 or higher, this
includes paths to transient programs.
put single quotes around arguments with semicolons in them,
so they don't turn into command delimiters.
The set command affects only the local shell's environment.
You can 'exit' to command.com and the original environment is
intact. The local environment is 2K large - which is
useful.
When using the Microsoft C compiler under pc-shell, the
compiler has a bad habit of look for parameters beginning
with forward slashes in the environment. If you get their
famous 'P0 : bad option' message, try revising the
environment.
Implementation notes Implementation notes
DOS doesn't acknowledge a 'change default drive' command
until you issue a 'get current directory' call. Why? The
only way I figured this out is by disassembling command.com.
PC|MS-DOS has a limit of 20 file handles. If you add a
command that opens files, make sure you catch the ctrl-break
signal and close them. Look at CAT.C or Y.C for examples.
DON'T REDIRECT INPUT INTO PRINT. Print gets all hosed up.
Print has lots of trouble in general with the pc-shell, and
should be avoided.
BUGS BUGS
Due to the way that environment strings are expanded on the
command line, semicolons inside shell variables look like
command seperators. If you enclose them in double quotes,
the problem will go away.
I have noticed intermittent problems running on an AT, with
DOS 3.0, but have been unable to reproduce them on a PC. I
suspect bugs in DOS 3.0 that are absent in 3.1. If you notice
any consistent problems, send me a bug report.
HISTORY HISTORY
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PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
V 2 0 V 2.0
Minor bug fixes. Started allocating command buffers out
of heap rather than stack, reducing stack usage. Stopped
releasing source with executables.
V 2 1 V 2.1
Fixed the bug that made "mv foo .." throw away the source
file and move it to "..foo", (i.e. nowhere). Added the
sh command, that allows you to run scripts without
re-invoking the shell.
V 2 2 V 2.2
Fixed the bug that locked pc up when a command line with
a leading ; was entered. Changed fork code so that files
with the extension .sh are run as scripts. The equals
sign in alias and set is now optional.
V 2 3 V 2.3
Removed information about versions 1.0 through 1.6 from
documentation, adding any relevant material to the tips
or implementation notes sections. Added redirection of
standard error, and checking for NOCLOBBER. Implemented
execution of the prompt string.
V 2 4 V 2.4
The problem running external programs written by IBM and
Microsoft has finally been traced to Aztecs fexecv
function. When is an ASCIIZ string not an ASCIIZ
string? When you need to put a single carriage return on
the end of it. THANKS to Programmers Journal. NOTE WELL
that needing a carriage return in your command tail for
EXEC calls is note documented in the IBM PC-DOS technical
reference.
All references to the Aztec screen library have been
removed, so this should work on Rainbows, Compupros,
AMPROs etc. etc. etc. ls is slower, but its a small
price to pay. If you want a fast version, one can be
created for you if you mail a contribution (hint,hint).
mv now will do the right thing when you try to move to a
drive that has been joined to a directory (DOS 3.1). It
also now has a verbose switch, which tells you what
exactly its doing. When I started writing a mv, I had no
idea how many special cases I would have to take care
of.
V 2 5 V 2.5
Problem with using the wrong path to search for external
programs solved. Main command line parsing changed so
that NOGLOB could be used to suppress file name
-14-
PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
expansion.
V 2 6 V 2.6
Many stupid bugs in 2.5 are addressed (sorry folks). I
now peek inside double quotes to do variable expansion.
Double quotes are now stripped.
V 2 7 V 2.7
Added read. Fixed bug in ls that would occasionally
leave you in a different directory. The exit command
will now just pop you out a level of shell execution,
rather than kicking you out to the DOS prompt.
V 2 8 V 2.8
Fixed bug in more that made it puke when you hit
<CTRL>-<BREAK> at the bottom of a screen-full. Made move
and cp preserve file times when they have to create a
target.
V 2 9 V 2.9
Fixed bug in ls that caused it to get confused when you
did an 'ls -R' on a drive other than default. Also,
stopped it from hanging on an empty pipe. Added the 'du'
command - which is simply the last line of ls -l. Shell
scripts will now be searched for on PATH.
DONATIONS REQUESTED DONATIONS REQUESTED
The shell seems to have generated an incredible amount of
interest, all around the country - someone apparently put
this code out over the usenet and arpanet, in addition to
its original FIDOnet roots.
I would like to keep working on it, but for it to
progress further, it can no longer be a 'lunch hour
hack.' I am therefore requesting that those who feel that
this is a useful piece of software send me a donation to
further my efforts towards purchasing a machine for home
use.
Anyone sending more that 25$ will recieve: 1. a PC-DOS
disk with most recent release full source and executable
image. 2. Source and executable for various other public
domain *nix programs (tail, nroff, cut, paste, diff,
grep)
If you use this every day, or if you are giving everyone
in your place of employment a copy, value it
accordingly.
This does not constitute a licensing agreement of any
sort, nor is any warranty implied. Once you have a copy
-15-
PC-SHELL (1) PC-DOS C Shell PC-SHELL (1)
of this program or its source, it's yours to hack to
pieces, use, revere, revile, or whatever. I like the
anarchic aspects of the various public domain networks.
QUESTIONS COMMENTS BUGREPORTS GOTO
KENT WILLIAMS
722 Rundell St.
Iowa City, IA 52240
(319) 338-6053 (HOME VOICE)
* UNIX is an unregistered trademark of AT&T.
-16-
