FTS(3) | Library Functions Manual | FTS(3) |
fts
, fts_open
,
fts_read
, fts_children
,
fts_set
, fts_close
—
#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);
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; /* file name */ 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_D
), all of these entries are terminal, that
is, they will not be revisited, nor will any of their descendants be
visited.
FTS_D
FTS_DC
FTS_DEFAULT
FTS_DNR
FTS_DOT
.
’ or
‘..
’ which was not specified as
a file name to fts_open
() (see
FTS_SEEDOT
).FTS_DP
FTS_D
.FTS_ERR
FTS_F
FTS_NS
FTS_NSOK
FTS_SL
FTS_SLNONE
FTS_W
fts_open
() as a
prefix.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
functions. It is initialized
to 0.fts
functions. It is initialized
to NULL
.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_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.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 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
NUL
-terminated.
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
FTS_LOGICAL
is
also specified.FTS_LOGICAL
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
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
fts
functions to set the fts_info field to
FTS_NSOK
and leave the contents of the
statp field undefined.FTS_PHYSICAL
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
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_WHITEOUT
FTS_XDEV
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.
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
() 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 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
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
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
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
fts_children
() or
fts_read
().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.
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
]fts
utility was expected to be included in the
IEEE Std 1003.1-1988 (“POSIX.1”)
revision. But twenty years later, it still was not included in the
IEEE Std 1003.1-2008 (“POSIX.1”)
revision.
March 30, 2011 | NetBSD 9.2 |