FTS(3) BSD Library Functions Manual FTS(3)
NAME
fts -- traverse a file hierarchy
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>
#include <fts.h>
FTS *
fts_open(char * const *path_argv, int options, int (*compar)(const FTSENT **, const FTSENT **));
FTSENT *
fts_read(FTS *ftsp);
FTSENT *
fts_children(FTS *ftsp, int options);
int
fts_set(FTS *ftsp, FTSENT *f, int options);
int
fts_close(FTS *ftsp);
DESCRIPTION
The fts functions are provided for traversing UNIX file hierarchies. A simple overview is that the
fts_open() function returns a ``handle'' on a file hierarchy, which is then supplied to the other fts
functions. The function fts_read() returns a pointer to a structure describing one of the files in the
file hierarchy. The function fts_children() returns a pointer to a linked list of structures, each of
which describes one of the files contained in a directory in the hierarchy. In general, directories
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 pos-sible possible
sible to walk the hierarchy ``logically'' (ignoring symbolic links) or physically (visiting symbolic
links), order the walk of the hierarchy or prune and/or re-visit portions of the hierarchy.
Two structures are defined (and typedef'd) in the include file <fts.h>. The first is FTS, the struc-ture structure
ture 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 hier-archy. hierarchy.
archy. 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 {
u_short fts_info; /* flags for FTSENT structure */
char *fts_accpath; /* access path */
char *fts_path; /* root path */
u_short fts_pathlen; /* strlen(fts_path) */
char *fts_name; /* file name */
u_short fts_namelen; /* strlen(fts_name) */
short fts_level; /* depth (-1 to N) */
int fts_errno; /* file errno */
long fts_number; /* local numeric value */
void *fts_pointer; /* local address value */
struct ftsent *fts_parent; /* parent directory */
struct ftsent *fts_link; /* next file structure */
struct ftsent *fts_cycle; /* cycle structure */
struct stat *fts_statp; /* stat(2) information */
} FTSENT;
These fields are defined as follows:
fts_info One of the following values describing the returned FTSENT structure and the file it rep-resents. represents.
resents. 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 pre-order.
FTS_DC A directory that causes a cycle in the tree. (The fts_cycle field of the
FTSENT structure will be filled in as well.)
FTS_DEFAULT Any FTSENT structure that represents a file type not explicitly described by
one of the other fts_info values.
FTS_DNR A directory which cannot be read. This is an error return, and the fts_errno
field will be set to indicate what caused the error.
FTS_DOT A file named `.' or `..' which was not specified as a file name to fts_open()
(see FTS_SEEDOT).
FTS_DP A directory being visited in post-order. The contents of the FTSENT struc-ture structure
ture will be unchanged from when it was returned in pre-order, i.e. with the
fts_info field set to FTS_D.
FTS_ERR This is an error return, and the fts_errno field will be set to indicate what
caused the error.
FTS_F A regular file.
FTS_NS A file for which no stat(2) information was available. The contents of the
fts_statp field are undefined. This is an error return, and the fts_errno
field will be set to indicate what caused the error.
FTS_NSOK A file for which no stat(2) information was requested. The contents of the
fts_statp field are undefined.
FTS_SL A symbolic link.
FTS_SLNONE A symbolic link with a non-existent target. The contents of the fts_statp
field reference the file characteristic information for the symbolic link
itself.
fts_accpath A path for accessing the file from the current directory.
fts_path The path for the file relative to the root of the traversal. This path contains the path
specified to fts_open() as a prefix.
fts_pathlen The length of the string referenced by fts_path.
fts_name The name of the file.
fts_namelen The length of the string referenced by fts_name.
fts_level 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 is num-bered numbered
bered FTS_ROOTPARENTLEVEL (-1), and the FTSENT structure for the root itself is numbered
FTS_ROOTLEVEL (0).
fts_errno Upon return of a FTSENT structure from the fts_children() or fts_read() functions, with
its fts_info field set to FTS_DNR, FTS_ERR or FTS_NS, the fts_errno field contains the
value of the external variable errno specifying the cause of the error. Otherwise, the
contents of the fts_errno field are undefined.
fts_number This field is provided for the use of the application program and is not modified by the
fts functions. It is initialized to 0.
fts_pointer This field is provided for the use of the application program and is not modified by the
fts functions. It is initialized to NULL.
fts_parent A pointer to the FTSENT 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 structure
for the initial entry point is provided as well, however, only the fts_level, fts_number
and fts_pointer fields are guaranteed to be initialized.
fts_link Upon return from the fts_children() function, the fts_link field points to the next struc-ture structure
ture in the NULL-terminated linked list of directory members. Otherwise, the contents of
the fts_link field are undefined.
fts_cycle 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 fts_cycle field
of the structure will point to the FTSENT structure in the hierarchy that references the
same file as the current FTSENT structure. Otherwise, the contents of the fts_cycle field
are undefined.
fts_statp 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 the file hierarchy. Therefore, the
fts_path and fts_accpath fields are guaranteed to be NUL-terminated only for the file most recently
returned by fts_read(). To use these fields to reference any files represented by other FTSENT struc-tures structures
tures will require that the path buffer be modified using the information contained in that FTSENT
structure's fts_pathlen field. Any such modifications should be undone before further calls to
fts_read() are attempted. The fts_name field is always NUL-terminated.
FTS_OPEN
The fts_open() 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 spec-ified. specified.
ified. The options are selected by or'ing the following values:
FTS_COMFOLLOW
This option causes any symbolic link specified as a root path to be followed immediately
whether or not FTS_LOGICAL is also specified.
FTS_LOGICAL This option causes the fts routines to return FTSENT structures for the targets of sym-bolic symbolic
bolic links instead of the symbolic links themselves. If this option is set, the only
symbolic links for which FTSENT structures are returned to the application are those ref-erencing referencing
erencing non-existent files. Either FTS_LOGICAL or FTS_PHYSICAL must be provided to the
fts_open() function.
FTS_NOCHDIR As a performance optimization, the fts functions change directories as they walk the file
hierarchy. This has the side-effect that an application cannot rely on being in any par-ticular particular
ticular directory during the traversal. The FTS_NOCHDIR option turns off this optimiza-tion, optimization,
tion, and the fts functions will not change the current directory. Note that applica-tions applications
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 fts_open().
FTS_NOSTAT By default, returned FTSENT structures reference file characteristic information (the
statp field) for each file visited. This option relaxes that requirement as a perfor-mance performance
mance optimization, allowing the fts functions to set the fts_info field to FTS_NSOK and
leave the contents of the statp field undefined.
FTS_PHYSICAL This option causes the fts routines to return FTSENT structures for symbolic links them-selves themselves
selves instead of the target files they point to. If this option is set, FTSENT struc-tures structures
tures for all symbolic links in the hierarchy are returned to the application. Either
FTS_LOGICAL or FTS_PHYSICAL must be provided to the fts_open() function.
FTS_SEEDOT By default, unless they are specified as path arguments to fts_open(), any files named
`.' or `..' encountered in the file hierarchy are ignored. This option causes the fts
routines to return FTSENT structures for them.
FTS_XDEV This option prevents fts from descending into directories that have a different device
number than the file from which the descent began.
The argument compar() specifies a user-defined function which may be used to order the traversal of the
hierarchy. It takes two pointers to pointers 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 file referenced by its second argument. The
fts_accpath, fts_path and fts_pathlen fields of the FTSENT structures may never be used in this compar-ison. comparison.
ison. If the fts_info field is set to FTS_NS or FTS_NSOK, the fts_statp field may not either. If the
compar() argument is NULL, the directory traversal order is in the order listed in path_argv for the
root paths, and in the order listed in the directory for everything else.
FTS_READ
The fts_read() function returns a pointer to an FTSENT structure describing a file in the hierarchy.
Directories (that are readable and do not cause 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 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, fts_read() returns NULL and sets the external
variable errno to 0. If an error unrelated to a file in the hierarchy occurs, fts_read() 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 not have been set (see fts_info).
The FTSENT structures returned by fts_read() may be overwritten after a call to fts_close() on the same
file hierarchy stream, or, after a call to fts_read() 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
fts_read() after the FTSENT structure has been returned by the function fts_read() in post-order.
FTS_CHILDREN
The fts_children() function returns a pointer to an FTSENT structure describing the first entry in a
NULL-terminated linked list of the files in the directory represented by the FTSENT structure most
recently returned by fts_read(). The list is linked through the fts_link field of the FTSENT struc-ture, structure,
ture, and is ordered by the user-specified comparison function, if any. Repeated calls to
fts_children() will recreate this linked list.
As a special case, if fts_read() has not yet been called for a hierarchy, fts_children() will return a
pointer to the files in the logical directory specified to fts_open(), i.e. the arguments specified to
fts_open(). Otherwise, if the FTSENT structure most recently returned by fts_read() is not a directory
being visited in pre-order, or the directory does not contain any files, fts_children() returns NULL
and sets errno to zero. If an error occurs, fts_children() returns NULL and sets errno appropriately.
The FTSENT structures returned by fts_children() may be overwritten after a call to fts_children(),
fts_close() or fts_read() on the same file hierarchy stream.
Option may be set to the following value:
FTS_NAMEONLY Only the names of the files are needed. The contents of all the fields in the returned
linked list of structures are undefined with the exception of the fts_name and
fts_namelen fields.
FTS_SET
The function fts_set() allows the user application to determine further processing for the file f of
the stream ftsp. The fts_set() function returns 0 on success, and -1 if an error occurs. Option must
be set to one of the following values:
FTS_AGAIN Re-visit the file; any file type may be re-visited. The next call to fts_read() will
return the referenced file. The fts_stat and fts_info 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 fts_read(). Normal use is for
post-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.
FTS_FOLLOW The referenced file must be a symbolic link. If the referenced file is the one most
recently returned by fts_read(), the next call to fts_read() returns the file with the
fts_info and fts_statp 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 fts_children(), the fts_info and fts_statp fields of the structure, when returned by
fts_read(), 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 fts_info field will be set to
FTS_SLNONE.
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.
FTS_SKIP No descendants of this file are visited. The file may be one of those most recently
returned by either fts_children() or fts_read().
FTS_CLOSE
The fts_close() function closes a file hierarchy stream ftsp and restores the current directory to the
directory from which fts_open() was called to open ftsp. The fts_close() function returns 0 on suc-cess, success,
cess, and -1 if an error occurs.
ERRORS
The function fts_open() may fail and set errno for any of the errors specified for the library func-tions functions
tions open(2) and malloc(3).
The function fts_close() may fail and set errno for any of the errors specified for the library func-tions functions
tions chdir(2) and close(2).
The functions fts_read() and fts_children() 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, fts_children(), fts_open() and fts_set() may fail and set errno as follows:
[EINVAL] The options were invalid.
SEE ALSO
find(1), chdir(2), stat(2), qsort(3)
STANDARDS
The fts utility is expected to be included in a future IEEE Std 1003.1-1988 (``POSIX.1'') revision.
BSD April 16, 1994 BSD
|