NAME
fts_open
,
fts_read
, fts_children
,
fts_set
, fts_close
—
traverse a file hierarchy
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 option);
int
fts_close
(FTS
*ftsp);
DESCRIPTION
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” (following symbolic links) or “physically” (not following 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 { unsigned 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) */ int 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 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
() (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, i.e., with the fts_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 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 numberedFTS_ROOTPARENTLEVEL
(-1), and theFTSENT
structure for the root itself is numberedFTS_ROOTLEVEL
(0). Note that while fts_level cannot hold a number of levels greater thanFTS_MAXLEVEL
, thefts
functions themselves are not limited to a fixed number of levels. Application code that inspects fts_level should be written with this in mind. - fts_errno
- Upon return of an
FTSENT
structure from thefts_children
() orfts_read
() functions, with its fts_info field set toFTS_DNR
,FTS_ERR
orFTS_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 toNULL
. - 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 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 theFTSENT
structure in the hierarchy that references the same file as the currentFTSENT
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
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
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 returnFTSENT
structures for the targets of symbolic links instead of the symbolic links themselves. If this option is set, the only symbolic links for whichFTSENT
structures are returned to the application are those referencing non-existent files. EitherFTS_LOGICAL
orFTS_PHYSICAL
must be provided to thefts_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. TheFTS_NOCHDIR
option turns off this optimization, and thefts
functions will not change the current directory. Note that applications should not themselves change their current directory and try to access files unlessFTS_NOCHDIR
is specified and absolute pathnames were provided as arguments tofts_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 thefts
functions to set the fts_info field toFTS_NSOK
and leave the contents of the statp field undefined. FTS_PHYSICAL
- This option causes the
fts
routines to returnFTSENT
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. EitherFTS_LOGICAL
orFTS_PHYSICAL
must be provided to thefts_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 thefts
routines to returnFTSENT
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.
If an error occurs,
fts_open
()
returns NULL
and sets errno
appropriately.
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
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.
options 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 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 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 fromfts_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 tofts_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 byfts_children
(), the fts_info and fts_statp fields of the structure, when returned byfts_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 toFTS_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
() orfts_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 the value 0 if
successful; otherwise the value -1 is returned and the global
variable errno is set to indicate the error.
ERRORS
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
function fchdir(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
] - A specified option is invalid or path_argv is empty.
SEE ALSO
HISTORY
The fts
functions first appeared in
4.3BSD-Reno. The interface was revised in
4.4BSD.