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FTS(3) UNIX Programmer's Manual FTS(3)
NNAAMMEE
ffttss - traverse a file hierarchy
SSYYNNOOPPSSIISS
##iinncclluuddee <<ssyyss//ttyyppeess..hh>>
##iinncclluuddee <<ssyyss//ssttaatt..hh>>
##iinncclluuddee <<ffttss..hh>>
_F_T_S _*
ffttss__ooppeenn(_c_h_a_r _* _c_o_n_s_t _*_p_a_t_h___a_r_g_v, _i_n_t _o_p_t_i_o_n_s,
_i_n_t _*_c_o_m_p_a_r_(_c_o_n_s_t _F_T_S_E_N_T _*_, _c_o_n_s_t _F_T_S_E_N_T _*_))
_F_T_S_E_N_T _*
ffttss__rreeaadd(_F_T_S _*_f_t_s_p)
_F_T_S_E_N_T _*
ffttss__cchhiillddrreenn(_F_T_S _*_f_t_s_p)
_i_n_t
ffttss__sseett(_F_T_S _f_t_s_p, _F_T_S_E_N_T _*_f, _i_n_t _o_p_t_i_o_n_s)
_i_n_t
ffttss__cclloossee(_F_T_S _*_f_t_s_p)
DDEESSCCRRIIPPTTIIOONN
The ffttss functions are provided for traversing UNIX file hierarchies.
The simple overview is that the ffttss__ooppeenn() function returns a ``handle''
on a file hierarchy, which is supplied to the other ffttss functions to de
termine which hierarchy they operate on. The function ffttss__rreeaadd() returns
a pointer to a structure describing one of the files in the file hierar
chy. The function ffttss__cchhiillddrreenn() returns a pointer to a linked list of
structures, each of which describes one of the files contained in a di
rectory in the hierarchy. In general, directories are visited two dis
tinguishable times; in preorder (before any of their descendants are
visited) and in postorder (after all of their descendants have been vis
ited). Files are visited once. It is possible to walk the hierarchy
``logically'' (ignoring symbolic links) or physically (visiting symbolic
links), order the walk of the hierarchy or prune and/or revisit portions
of the hierarchy.
Two structures are defined (and typedef'd) in the include file <_f_t_s_._h>.
The first is _F_T_S, the structure that represents the file hierarchy
stream. The second is _F_T_S_E_N_T, the structure that represents a file in
the file hierarchy. Normally, an _F_T_S_E_N_T structure is returned for every
file in the file hierarchy. In this manual page, ``file'' and ``_F_T_S_E_N_T
structure'' are generally interchangeable. The _F_T_S_E_N_T structure contains
at least the following fields, which are described in greater detail be
low:
typedef struct _ftsent {
u_short fts_info; /* flags for FTSENT structure */
char *fts_accpath; /* access path */
char *fts_path; /* root path */
short fts_pathlen; /* strlen(fts_path) */
char *fts_name; /* file name */
short fts_namelen; /* strlen(fts_name) */
short fts_level; /* depth (-1 to N) */
long fts_number; /* local numeric value */
void *fts_pointer; /* local address value */
struct ftsent *fts_parent; /* parent directory */
struct ftsent *fts_link; /* cycle or next file structure */
struct stat fts_statb; /* stat(2) information */
} FTSENT;
These fields are defined as follows:
_f_t_s___i_n_f_o One of the following flags describing the returned _F_T_S_E_N_T
structure and the file it represents. With the exception of
directories without errors (FTS_D), all of these entries are
terminal, that is, they will not be revisited, nor will any
of their descendants be visited.
FTS_D A directory being visited in preorder.
FTS_DC A directory that causes a cycle in the tree.
(The _f_t_s___l_i_n_k field of the _F_T_S_E_N_T structure
will be filled in as well.)
FTS_DEFAULT Any _F_T_S_E_N_T structure that represents a file
type not explicitly described by one of the
other _f_t_s___i_n_f_o values.
FTS_DNR A directory which cannot be read. An error re
turn; the external variable _e_r_r_n_o will be set
to indicate the error.
FTS_DOT A file named `.' or `..' which was not speci
fied as a file name to ffttss__ooppeenn() (see
FTS_SEEDOT).
FTS_DP A directory being visited in postorder. The
contents of the _F_T_S_E_N_T structure will be un
changed from when it was returned in preorder,
i.e. with the _f_t_s___i_n_f_o field set to FTS_D.
FTS_ERR An error return; the external variable _e_r_r_n_o
will be set to indicate the error.
FTS_F A regular file.
FTS_NS A file for which no stat(2) information was
available. The contents of the _f_t_s___s_t_a_t_b field
are undefined. An error return; the external
variable _e_r_r_n_o will be set to indicate the er
ror.
FTS_NSOK A file for which no stat(2) information was re
quested. The contents of the _f_t_s___s_t_a_t_b field
are undefined.
FTS_SL A symbolic link.
FTS_SLNONE A symbolic link with a nonexistent target.
The contents of the _f_t_s___s_t_a_t_b field contain the
file characteristic information for the symbol
ic link itself.
_f_t_s___a_c_c_p_a_t_h A path for accessing the file from the current directory.
_f_t_s___p_a_t_h The path for the file relative to the root of the traversal.
This path contains the path specified to ffttss__ooppeenn() as a
prefix.
_f_t_s___p_a_t_h_l_e_n The length of the string referenced by _f_t_s___p_a_t_h.
_f_t_s___n_a_m_e The name of the file.
_f_t_s___n_a_m_e_l_e_n The length of the string referenced by _f_t_s___n_a_m_e.
_f_t_s___l_e_v_e_l The depth of the traversal, numbered from -1 to N, where
this file was found. The _F_T_S_E_N_T structure representing the
parent of the starting point (or root) of the traversal is
numbered -1, and the _F_T_S_E_N_T structure for the root itself is
numbered 0.
_f_t_s___n_u_m_b_e_r This field is provided for the use of the application pro
gram and is not modified by the ffttss functions. It is ini
tialized to 0. The fields _f_t_s___n_u_m_b_e_r and _f_t_s___p_o_i_n_t_e_r occupy
the same physical location; using both may cause undefined
results.
_f_t_s___p_o_i_n_t_e_r This field is provided for the use of the application pro
gram and is not modified by the ffttss functions. It is ini
tialized to NULL. The fields _f_t_s___n_u_m_b_e_r and _f_t_s___p_o_i_n_t_e_r oc
cupy the same physical location; using both may cause unde
fined results.
_f_t_s___p_a_r_e_n_t A pointer to the _F_T_S_E_N_T structure referencing the file in
the hierarchy immediately above the current file, i.e. the
directory of which this file is a member. A parent struc
ture for the initial entry point is provided as well, howev
er, only the _f_t_s___l_e_v_e_l, _f_t_s___n_u_m_b_e_r and _f_t_s___p_o_i_n_t_e_r fields
are guaranteed to be initialized.
_f_t_s___l_i_n_k The _f_t_s___l_i_n_k field has two separate uses. If a directory
causes a cycle in the hierarchy (see FTS_DC), either because
of a hard link between two directories, or a symbolic link
pointing to a directory, the _f_t_s___l_i_n_k field of the structure
will point to the _F_T_S_E_N_T structure in the hierarchy that
references the same file as the current _F_T_S_E_N_T structure.
Also, upon return from the ffttss__cchhiillddrreenn() function, the
_f_t_s___l_i_n_k field points to the next structure in the linked
list of directory members. Otherwise, the contents of the
_f_t_s___l_i_n_k field are undefined.
_f_t_s___s_t_a_t_b Stat(2) information for the file.
FFTTSS__OOPPEENN
The ffttss__ooppeenn() function takes a pointer to an array of character pointers
naming one or more paths which make up a logical file hierarchy to be
traversed. The array must be terminated by a NULL pointer.
There are a number of options, at least one of which (either FTS_LOGICAL
or FTS_PHYSICAL) must be specified. The options are selected by _o_r'ing
the following values:
FTS_LOGICAL This option causes the ffttss routines to return _F_T_S_E_N_T struc
tures for the targets of symbolic links instead of the sym
bolic links themselves. If this option is set, the only
symbolic links for which _F_T_S_E_N_T structures are returned to
the application are those referencing nonexistent files.
Either FTS_LOGICAL or FTS_PHYSICAL _m_u_s_t be provided to the
ffttss__ooppeenn() function.
FTS_NOCHDIR As a performance optimization, the ffttss functions change di
rectories as they walk the file hierarchy. This has the
sideeffect that an application cannot rely on being in any
particular directory during the traversal. The FTS_NOCHDIR
option turns off this optimization, and the ffttss functions
will not change the current directory. Note that applica
tions should not themselves change their current directory
and try to access files unless FTS_NOCHDIR is specified and
absolute pathnames were provided as arguments to
ffttss__ooppeenn().
FTS_NOSTAT By default, returned _F_T_S_E_N_T structures contain file charac
teristic information (the _s_t_a_t_b field) for each file visit
ed. This option relaxes that requirement as a performance
optimization, allowing the ffttss functions to set the
_f_t_s___i_n_f_o field to FTS_NSOK and leave the contents of the
_s_t_a_t_b field undefined.
FTS_PHYSICAL This option causes the ffttss routines to return _F_T_S_E_N_T struc
tures for symbolic links themselves instead of the target
files they point to. If this option is set, _F_T_S_E_N_T struc
tures for all symbolic links in the hierarchy are returned
to the application. Either FTS_LOGICAL or FTS_PHYSICAL
_m_u_s_t be provided to the ffttss__ooppeenn() function.
FTS_SEEDOT By default, unless they are specified as path arguments to
ffttss__ooppeenn(), any files named `.' and `..' encountered in the
file hierarchy are ignored. This option causes the ffttss
routines to return _F_T_S_E_N_T structures for them.
FTS_XDEV This option prevents ffttss from descending into directories
that have a different device number than the file from
which the descent began.
The argument ccoommppaarr() specifies a userdefined function which may be used
to order the traversal of the hierarchy. It takes two pointers to point
ers to _F_T_S_E_N_T structures as arguments and should return a negative value,
zero, or a positive value to indicate if the file referenced by its first
argument comes before, in any order with respect to, or after, the file
referenced by its second argument. The _f_t_s___a_c_c_p_a_t_h, _f_t_s___p_a_t_h and
_f_t_s___p_a_t_h_l_e_n fields of the _F_T_S_E_N_T structures may _n_e_v_e_r be used in this
comparison. If the _f_t_s___i_n_f_o field is set to FTS_NS or the _f_t_s___s_t_a_b field
may not either. If the ccoommppaarr() argument is NULL, the directory traver
sal order is unspecified except for the root paths which are traversed in
the order listed in _p_a_t_h___a_r_g_v.
FFTTSS__RREEAADD
The ffttss__rreeaadd() function returns a pointer to an _F_T_S_E_N_T structure describ
ing a file in the hierarchy. Directories (that are readable and do not
cause cycles) are visited at least twice, once in preorder and once in
postorder. All other files are visited at least once. (Hard links be
tween directories that do not cause cycles or symbolic links to symbolic
links may cause files to be visited more than once, or directories more
than twice.)
If all the members of the hierarchy have been returned, ffttss__rreeaadd() re
turns NULL and sets the external variable _e_r_r_n_o to 0. If an error unre
lated to a file in the hierarchy occurs, ffttss__rreeaadd() returns NULL and sets
_e_r_r_n_o appropriately. If an error related to a returned file occurs, a
pointer to an _F_T_S_E_N_T structure is returned, and _e_r_r_n_o may or may not have
been set (see _f_t_s___i_n_f_o).
The _F_T_S_E_N_T structures returned by ffttss__rreeaadd() may be overwritten after a
call to ffttss__cclloossee() on the same file hierarchy stream, or, after a call
to ffttss__rreeaadd() on the same file hierarchy stream unless they represent a
file of type directory, in which case they will not be overwritten until
after a call to ffttss__rreeaadd() after the _F_T_S_E_N_T structure has been returned
by the function ffttss__rreeaadd() in postorder.
FFTTSS__CCHHIILLDDRREENN
The ffttss__cchhiillddrreenn() function returns a pointer to an _F_T_S_E_N_T structure de
scribing the first entry in a linked list of the files in the directory
represented by the _F_T_S_E_N_T structure most recently returned by ffttss__rreeaadd().
The list is linked through the _f_t_s___l_i_n_k field of the _F_T_S_E_N_T structure,
and is ordered by the userspecified comparison function, if any. Re
peated calls to ffttss__cchhiillddrreenn() will recreate this linked list.
If the _F_T_S_E_N_T structure most recently returned by ffttss__rreeaadd() is not a di
rectory being visited in preorder, or the directory does not contain any
files, ffttss__cchhiillddrreenn() returns NULL and sets _e_r_r_n_o to zero. If an error
occurs, ffttss__cchhiillddrreenn() returns NULL and sets _e_r_r_n_o appropriately.
The _F_T_S_E_N_T structures returned by ffttss__cchhiillddrreenn() may be overwritten after
a call to ffttss__cclloossee() on the same file hierarchy stream, or after a call
to ffttss__cchhiillddrreenn() or ffttss__rreeaadd() on the same file hierarchy stream.
A single buffer is used for all of the paths of all of the files in the
file hierarchy. Therefore, the _f_t_s___p_a_t_h and _f_t_s___a_c_c_p_a_t_h fields are guar
anteed to be NULLterminated _o_n_l_y for the file most recently returned by
ffttss__rreeaadd(). To use these fields to reference any files represented by
other _F_T_S_E_N_T structures will require that the path buffer be modified us
ing the information contained in that _F_T_S_E_N_T structure's _f_t_s___p_a_t_h_l_e_n
field. Any such modifications should be undone before further calls to
ffttss__rreeaadd() are attempted. The _f_t_s___n_a_m_e field is always NULLterminated.
FFTTSS__SSEETT
The function ffttss__sseett() allows the user application to determine further
processing for the file _f of the stream _f_t_s_p. The ffttss__sseett() function re
turns 0 on success, and -1 if an error occurs. _O_p_t_i_o_n must be set to one
of the following values:
FTS_AGAIN Revisit the file; any file type may be revisited. The
next call to ffttss__rreeaadd() will return the referenced file.
The _f_t_s___s_t_a_t and _f_t_s___i_n_f_o fields of the structure will be
reinitialized at that time, but no other fields will have
been changed. This option is meaningful only for the most
recently returned file from ffttss__rreeaadd(). Normal use is for
postorder directory visits, where it causes the directory
to be revisited (in both pre and postorder) as well as
all of its descendants.
FTS_FOLLOW The referenced file must be a symbolic link. If the refer
enced file is the one most recently returned by ffttss__rreeaadd(),
the next call to ffttss__rreeaadd() returns the file with the
_f_t_s___i_n_f_o and _f_t_s___s_t_a_t_b fields reinitialized to reflect the
target of the symbolic link instead of the symbolic link
itself. If the file is one of those most recently returned
by ffttss__cchhiillddrreenn(), the _f_t_s___i_n_f_o and _f_t_s___s_t_a_t_b fields of the
structure, when returned by ffttss__rreeaadd(), will reflect the
target of the symbolic link instead of the symbolic link
itself. In either case, if the target of the symbolic link
does not exist the fields of the returned structure will be
unchanged and the _f_t_s___i_n_f_o field will be set to FTS_SLNONE.
If the target of the link is a directory, the preorder re
turn, followed by the return of all of its descendants,
followed by a postorder return, is done.
FTS_SKIP No descendants of this file are visited. The file may be
one of those most recently returned by either
ffttss__cchhiillddrreenn() or ffttss__rreeaadd().
FFTTSS__CCLLOOSSEE
The ffttss__cclloossee() function closes a file hierarchy stream _f_t_s_p and restores
the current directory to the directory from which ffttss__ooppeenn() was called
to open _f_t_s_p. The ffttss__cclloossee() function returns 0 on success, and -1 if an
error occurs.
EERRRROORRSS
The function ffttss__ooppeenn() may fail and set errno for any of the errors
specified for the library functions open(2) and malloc(3).
The function ffttss__cclloossee() may fail and set errno for any of the errors
specified for the library functions chdir(2) and close(2).
The functions FFttss__rreeaadd() and ffttss__cchhiillddrreenn() may fail and set errno for
any of the errors specified for the library functions chdir(2),
malloc(3), opendir(3), readdir(3) and stat(2).
SSEEEE AALLSSOO
find(1), chdir(2), stat(2), qsort(3)
SSTTAANNDDAARRDDSS
The ffttss utility is expected to be a superset of the IEEE Std1003.11988
(``POSIX'') specification.
BSD Experimental July 31, 1991 6
