fts , fts_open , fts_read , fts_children , fts_set , fts_close — 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 | options) ; |
int
fts_close( |
FTS * | ftsp) ; |
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 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 */
|
|
short |
fts_pathlen ; |
/* strlen(fts_path) */
|
||
char | * |
fts_name ; |
/* filename */
|
|
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 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 pre-order.
FTS_DC
A directory that causes a cycle in the tree. (The
fts_cycle
field of theFTSENT
structure will be filled in as well.)FTS_DEFAULT
Any
FTSENT
structure that represents a file type not explicitly described by one of the otherfts_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 filename to
fts_open
() (seeFTS_SEEDOT
).FTS_DP
A directory being visited in post-order. The contents of the
FTSENT
structure will be unchanged from when it was returned in pre-order, that is, with thefts_info
field set toFTS_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 thefts_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 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,
that is, 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
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 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.
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 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 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.
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.
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
(), that
is, 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.
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
().
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,
and −1 if an error occurs.
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:
The options were invalid.
find(1), chdir(2), stat(2), ftw(3), qsort(3)
$NetBSD: fts.3,v 1.13.2.1 1997/11/14 02:09:32 mrg Exp $ Copyright (c) 1989, 1991, 1993, 1994 The Regents of the University of California. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. All advertising materials mentioning features or use of this software must display the following acknowledgement: This product includes software developed by the University of California, Berkeley and its contributors. 4. Neither the name of the University nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. (#)fts.3 8.5 (Berkeley) 4/16/94 |