NAME
ffttss - traverse a file hierarchy
LLIIBBRRAARRYYStandard C Library (libc, -lc)
SYNOPSIS
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FTS * ffttssooppeenn(char * const *pathargv, int options, int (*compar)(const FTSENT **, const FTSENT **)); FTSENT *> ffttssrreeaadd(FTS *ftsp);
FTSENT *ffttsscchhiillddrreenn(FTS *ftsp, int options);
intffttsssseett(FTS *ftsp, FTSENT *f, int options);
intffttsscclloossee(FTS *ftsp);
DESCRIPTION
The ffttss functions are provided for traversing UNIX file hierarchies. A simple overview is that the ffttssooppeenn() function returns a ``handle'' on a file hierarchy, which is then supplied to the other ffttss functions. The function ffttssrreeaadd() returns a pointer to a structure describing one of the files in the file hierarchy. The function ffttsscchhiillddrreenn() returns a pointer to a linked list of structures, each of which describes one ofthe files contained in a directory in the hierarchy. In general, direc-
tories are visited two distinguishable times; in pre-order (before any of
their descendants are visited) and in post-order (after all of their
descendants have been visited). Files are visited once. It is possibleto walk the hierarchy ``logically'' (ignoring symbolic links) or physi-
cally (visiting symbolic links), order the walk of the hierarchy or pruneand/or re-visit portions of the hierarchy.
Two structures are defined (and typedef'd) in the include file
The first is FTS, the structure that represents the file hierarchy itself. The second is FTSENT, the structure that represents a file in the file hierarchy. Normally, an FTSENT structure is returned for every file in the file hierarchy. In this manual page, ``file'' and ``FTSENT structure'' are generally interchangeable. The FTSENT structure contains at least the following fields, which are described in greater detail below:. typedef struct ftsent {
ushort ftsinfo; /* flags for FTSENT structure */
char *ftsaccpath; /* access path */
char *ftspath; /* root path */
ushort ftspathlen; /* strlen(ftspath) */
char *ftsname; /* file name */
ushort ftsnamelen; /* strlen(ftsname) */
short ftslevel; /* depth (-1 to N) */
int ftserrno; /* file errno */
long ftsnumber; /* local numeric value */
void *ftspointer; /* local address value */
struct ftsent *ftsparent; /* parent directory */
struct ftsent *ftslink; /* next file structure */
struct ftsent *ftscycle; /* cycle structure */
struct stat *ftsstatp; /* stat(2) information */
} FTSENT; These fields are defined as follows:ftsinfo One of the following values describing the returned FTSENT
structure and the file it represents. With the exception of directories without errors (FTSD), all of these entries are terminal, that is, they will not be revisited, nor will any of their descendants be visited.FTSD A directory being visited in pre-order.
FTSDC A directory that causes a cycle in the tree.(The ftscycle field of the FTSENT structure
will be filled in as well.) FTSDEFAULT Any FTSENT structure that represents a file type not explicitly described by one of theother ftsinfo values.
FTSDNR A directory which cannot be read. This is anerror return, and the ftserrno field will be
set to indicate what caused the error.FTSDOT A file named `.' or `..' which was not speci-
fied as a file name to ffttssooppeenn() (see FTSSEEDOT).FTSDP A directory being visited in post-order. The
contents of the FTSENT structure will beunchanged from when it was returned in pre-
order, i.e. with the ftsinfo field set to
FTSD.FTSERR This is an error return, and the ftserrno
field will be set to indicate what caused the error. FTSF A regular file. FTSNS A file for which no stat(2) information wasavailable. The contents of the ftsstatp field
are undefined. This is an error return, andthe ftserrno field will be set to indicate
what caused the error. FTSNSOK A file for which no stat(2) information wasrequested. The contents of the ftsstatp field
are undefined. FTSSL A symbolic link.FTSSLNONE A symbolic link with a non-existent target.
The contents of the ftsstatp field reference
the file characteristic information for the symbolic link itself.ftsaccpath A path for accessing the file from the current directory.
ftspath The path for the file relative to the root of the traversal.
This path contains the path specified to ffttssooppeenn() as a prefix.ftspathlen The length of the string referenced by ftspath.
ftsname The name of the file.
ftsnamelen The length of the string referenced by ftsname.
ftslevel The depth of the traversal, numbered from -1 to N, where
this file was found. The FTSENT structure representing the parent of the starting point (or root) of the traversal isnumbered FTSROOTPARENTLEVEL (-1), and the FTSENT structure
for the root itself is numbered FTSROOTLEVEL (0).ftserrno Upon return of a FTSENT structure from the ffttsscchhiillddrreenn() or
ffttssrreeaadd() functions, with its ftsinfo field set to
FTSDNR, FTSERR or FTSNS, the ftserrno field contains the
value of the external variable errno specifying the cause ofthe error. Otherwise, the contents of the ftserrno field
are undefined.ftsnumber 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.ftspointer 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.ftsparent A pointer to the FTSENT structure referencing the file in
the hierarchy immediately above the current file, i.e. thedirectory of which this file is a member. A parent struc-
ture for the initial entry point is provided as well, how-
ever, only the ftslevel, ftsnumber and ftspointer fields
are guaranteed to be initialized.ftslink Upon return from the ffttsscchhiillddrreenn() function, the ftslink
field points to the next structure in the NULL-terminated
linked list of directory members. Otherwise, the contentsof the ftslink field are undefined.
ftscycle If a directory causes a cycle in the hierarchy (see FTSDC),
either because of a hard link between two directories, or asymbolic link pointing to a directory, the ftscycle field
of the structure will point to the FTSENT structure in the hierarchy that references the same file as the currentFTSENT structure. Otherwise, the contents of the ftscycle
field are undefined.ftsstatp A pointer to stat(2) information for the file.
A single buffer is used for all of the paths of all of the files in thefile hierarchy. Therefore, the ftspath and ftsaccpath fields are guar-
anteed to be NUL-terminated only for the file most recently returned by
ffttssrreeaadd(). To use these fields to reference any files represented by other FTSENT structures will require that the path buffer be modifiedusing the information contained in that FTSENT structure's ftspathlen
field. Any such modifications should be undone before further calls toffttssrreeaadd() are attempted. The ftsname field is always NUL-terminated.
FFTTSSOOPPEENN The ffttssooppeenn() 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 FTSLOGICAL or FTSPHYSICAL) must be specified. The options are selected by or'ing the following values: FTSCOMFOLLOW This option causes any symbolic link specified as a root path to be followed immediately whether or not FTSLOGICAL is also specified.FTSLOGICAL This option causes the ffttss routines to return FTSENT 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 FTSENT structures are returned tothe application are those referencing non-existent files.
Either FTSLOGICAL or FTSPHYSICAL must be provided to the ffttssooppeenn() function. FTSNOCHDIR As a performance optimization, the ffttss functions change directories as they walk the file hierarchy. This has theside-effect that an application cannot rely on being in any
particular directory during the traversal. The FTSNOCHDIR option turns off this optimization, and the ffttss functionswill not change the current directory. Note that applica-
tions should not themselves change their current directory and try to access files unless FTSNOCHDIR is specified and absolute pathnames were provided as arguments to ffttssooppeenn().FTSNOSTAT By default, returned FTSENT structures reference file char-
acteristic information (the statp field) for each file vis-
ited. This option relaxes that requirement as a perfor-
mance optimization, allowing the ffttss functions to set theftsinfo field to FTSNSOK and leave the contents of the
statp field undefined.FTSPHYSICAL This option causes the ffttss routines to return FTSENT struc-
tures for symbolic links themselves instead of the targetfiles they point to. If this option is set, FTSENT struc-
tures for all symbolic links in the hierarchy are returned to the application. Either FTSLOGICAL or FTSPHYSICAL must be provided to the ffttssooppeenn() function. FTSSEEDOT By default, unless they are specified as path arguments to ffttssooppeenn(), any files named `.' or `..' encountered in the file hierarchy are ignored. This option causes the ffttss routines to return FTSENT structures for them. FTSXDEV 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 user-defined function which may be used
to order the traversal of the hierarchy. It takes two pointers to point-
ers to FTSENT 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 filereferenced by its second argument. The ftsaccpath, ftspath and
ftspathlen fields of the FTSENT structures may never be used in this
comparison. If the ftsinfo field is set to FTSNS or FTSNSOK, the
ftsstatp field may not either. If the ccoommppaarr() argument is NULL, the
directory traversal order is in the order listed in pathargv for the root paths, and in the order listed in the directory for everything else. FFTTSSRREEAADDThe ffttssrreeaadd() function returns a pointer to an FTSENT structure describ-
ing a file in the hierarchy. Directories (that are readable and do notcause cycles) are visited at least twice, once in pre-order and once in
post-order. All other files are visited at least once. (Hard links
between directories that do not cause cycles or symbolic links to sym-
bolic 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, ffttssrreeaadd() returns NULL and sets the external variable errno to 0. If an error unrelated to a file in the hierarchy occurs, ffttssrreeaadd() returns NULL and sets errno appropriately. If an error related to a returned file occurs, a pointer to an FTSENT structure is returned, and errno may or may nothave been set (see ftsinfo).
The FTSENT structures returned by ffttssrreeaadd() may be overwritten after a call to ffttsscclloossee() on the same file hierarchy stream, or, after a call to ffttssrreeaadd() 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 ffttssrreeaadd() after the FTSENT structure has been returnedby the function ffttssrreeaadd() in post-order.
FFTTSSCCHHIILLDDRREENN The ffttsscchhiillddrreenn() function returns a pointer to an FTSENT structuredescribing the first entry in a NULL-terminated linked list of the files
in the directory represented by the FTSENT structure most recentlyreturned by ffttssrreeaadd(). The list is linked through the ftslink field of
the FTSENT structure, and is ordered by the user-specified comparison
function, if any. Repeated calls to ffttsscchhiillddrreenn() will recreate this linked list. As a special case, if ffttssrreeaadd() has not yet been called for a hierarchy,ffttsscchhiillddrreenn() will return a pointer to the files in the logical direc-
tory specified to ffttssooppeenn(), i.e. the arguments specified to ffttssooppeenn(). Otherwise, if the FTSENT structure most recently returned by ffttssrreeaadd()is not a directory being visited in pre-order, or the directory does not
contain any files, ffttsscchhiillddrreenn() returns NULL and sets errno to zero.If an error occurs, ffttsscchhiillddrreenn() returns NULL and sets errno appropri-
ately. The FTSENT structures returned by ffttsscchhiillddrreenn() may be overwritten after a call to ffttsscchhiillddrreenn(), ffttsscclloossee() or ffttssrreeaadd() on the same file hierarchy stream. Option may be set to the following value:FTSNAMEONLY Only the names of the files are needed. The contents of
all the fields in the returned linked list of structuresare undefined with the exception of the ftsname and
ftsnamelen fields.
FFTTSSSSEETT The function ffttsssseett() allows the user application to determine furtherprocessing for the file f of the stream ftsp. The ffttsssseett() function
returns 0 on success, and -1 if an error occurs. Option must be set to
one of the following values:FTSAGAIN Re-visit the file; any file type may be re-visited. The
next call to ffttssrreeaadd() will return the referenced file.The ftsstat and ftsinfo 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 ffttssrreeaadd(). Normal use is forpost-order directory visits, where it causes the directory
to be re-visited (in both pre and post-order) as well as
all of its descendants.FTSFOLLOW The referenced file must be a symbolic link. If the refer-
enced file is the one most recently returned by ffttssrreeaadd(), the next call to ffttssrreeaadd() returns the file with theftsinfo and ftsstatp 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 returnedby ffttsscchhiillddrreenn(), the ftsinfo and ftsstatp fields of the
structure, when returned by ffttssrreeaadd(), 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 beunchanged and the ftsinfo field will be set to FTSSLNONE.
If the target of the link is a directory, the pre-order
return, followed by the return of all of its descendants,followed by a post-order return, is done.
FTSSKIP No descendants of this file are visited. The file may be one of those most recently returned by either ffttsscchhiillddrreenn() or ffttssrreeaadd(). FFTTSSCCLLOOSSEEThe ffttsscclloossee() function closes a file hierarchy stream ftsp and restores
the current directory to the directory from which ffttssooppeenn() was calledto open ftsp. The ffttsscclloossee() function returns 0 on success, and -1 if
an error occurs. EERRRROORRSS The function ffttssooppeenn() may fail and set errno for any of the errors specified for the library functions open(2) and malloc(3). The function ffttsscclloossee() may fail and set errno for any of the errors specified for the library functions chdir(2) and close(2). The functions ffttssrreeaadd() and ffttsscchhiillddrreenn() 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). In addition, ffttsscchhiillddrreenn(), ffttssooppeenn() and ffttsssseett() may fail and set errno as follows: [EINVAL] The options were invalid.SEE ALSO
find(1), chdir(2), stat(2), qsort(3) STANDARDS The ffttss utility is expected to be included in a future IEEE Std1003.1-1988 (``POSIX.1'') revision.
BSD April 16, 1994 BSD