fts - traverse a file hierarchy
#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 option);
int
fts_close(FTS *ftsp);
The fts functions are provided for traversing UNIX file hierarchies. 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 within 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 possible 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 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 {
u_short fts_info; /* flags for FTSENT
structure */
char *fts_accpath; /* access path */
char *fts_path; /* root path */
size_t fts_pathlen; /* strlen(fts_path)
*/
char *fts_name; /* file name */
size_t 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 flags describing the returned FTSENT
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 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 postorder. The
contents of the FTSENT structure
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
numbered -1, and the FTSENT structure for the
root itself is
numbered 0.
fts_errno Upon return of an 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 structure in the nullterminated
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 null terminated only for the file most recently
returned by
fts_read(). To use these fields to reference any files represented by
other FTSENT structures 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 null
terminated.
FTS_OPEN [Toc] [Back]
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 specified. 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 symbolic 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 referencing 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
particular directory during the traversal.
The FTS_NOCHDIR
option turns off this optimization, and the
fts functions
will not change the current directory. Note
that applications
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 performance
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 themselves instead of
the target
files they point to. If this option is set,
FTSENT structures
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 compar argument 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
comparison. 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 [Toc] [Back]
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 [Toc] [Back]
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 structure, 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 0. 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 [Toc] [Back]
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 or -1 if an error occurred. option must
be set to one
of the following values:
FTS_AGAIN Re-visit the file; any file type may be revisited. 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 [Toc] [Back]
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 success
or -1 if an
error occurred.
The function fts_open() may fail and set errno for any of
the errors
specified for the library functions open(2) and malloc(3).
The function fts_close() may fail and set errno for any of
the errors
specified for the library functions 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 specified option is invalid.
find(1), chdir(2), stat(2), qsort(3)
The fts utility is expected to be included in a future IEEE
Std
1003.1-1988 (``POSIX'') revision.
OpenBSD 3.6 April 16, 1994
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