fts(3) - Linux manual page (original) (raw)
fts(3) Library Functions Manual fts(3)
NAME top
fts, fts_open, fts_read, fts_children, fts_set, fts_close -
traverse a file hierarchyLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <sys/types.h>**
**#include <sys/stat.h>**
**#include <fts.h>**
**FTS *fts_open(char *const ***_pathargv_**, int** _options_**,**
**typeof(int (const FTSENT , const FTSENT ))**
***_Nullable** _compar_**);**
**FTSENT *fts_read(FTS ***_ftsp_**);**
**FTSENT *fts_children(FTS ***_ftsp_**, int** _instr_**);**
**int fts_set(FTS ***_ftsp_**, FTSENT ***_f_**, int** _instr_**);**
**int fts_close(FTS ***_ftsp_**);**DESCRIPTION top
The fts functions are provided for traversing file hierarchies. A
simple overview is that the **fts_open**() function returns a "handle"
(of type _FTS *_) that refers to a file hierarchy "stream". This
handle 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
preorder (before any of their descendants are visited) and in
postorder (after all of their descendants have been visited).
Files are visited once. It is possible to walk the hierarchy
"logically" (visiting the files that symbolic links point to) or
physically (visiting the symbolic links themselves), order the
walk of the hierarchy or prune and/or revisit portions of the
hierarchy.
Two structures (and associated types) are defined in the include
file _<fts.h>_. The first type is _FTS_, the structure that
represents the file hierarchy itself. The second type 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 fields describing a file. The
structure contains at least the following fields (there are
additional fields that should be considered private to the
implementation):
typedef struct _ftsent {
unsigned short fts_info; /* flags for FTSENT structure */
char *fts_accpath; /* access path */
char *fts_path; /* root path */
short fts_pathlen; /* strlen(fts_path) +
strlen(fts_name) */
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; /* [l]stat(2) information */
} FTSENT;
These fields are defined as follows:
_ftsinfo_
One of the following values 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
_ftscycle_ 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 _ftsinfo_
values.
**FTS_DNR**
A directory which cannot be read. This is an error
return, and the _ftserrno_ 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**() (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 preorder, that is, with
the _ftsinfo_ field set to **FTS_D**.
**FTS_ERR**
This is an error return, and the _ftserrno_ field
will be set to indicate what caused the error.
**FTS_F** A regular file.
**FTS_NS** A file for which no [**l**][stat(2)](../man2/stat.2.html) information was
available. The contents of the _ftsstatp_ field are
undefined. This is an error return, and the
_ftserrno_ field will be set to indicate what caused
the error.
**FTS_NSOK**
A file for which no [**l**][stat(2)](../man2/stat.2.html) information was
requested. The contents of the _ftsstatp_ field are
undefined.
**FTS_SL** A symbolic link.
**FTS_SLNONE**
A symbolic link with a nonexistent target. The
contents of the _ftsstatp_ field reference the file
characteristic information for the symbolic link
itself.
_ftsaccpath_
A path for accessing the file from the current directory.
_ftspath_
The path for the file relative to the root of the
traversal. This path contains the path specified to
**fts_open**() as a prefix.
_ftspathlen_
The sum of the lengths of the strings referenced by
_ftspath_ and _ftsname_.
_ftsname_
The name of the file.
_ftsnamelen_
The length of the string referenced by _ftsname_.
_ftslevel_
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.
_ftserrno_
If **fts_children**() or **fts_read**() returns an _FTSENT_ structure
whose _ftsinfo_ field is set to **FTS_DNR**, **FTS_ERR**, or **FTS_NS**,
the _ftserrno_ field contains the error number (i.e., the
_[errno](../man3/errno.3.html)_ value) specifying the error. Otherwise, the contents
of the _ftserrno_ field are undefined.
_ftsnumber_
This field is provided for the use of the application
program and is not modified by the fts functions. It is
initialized to 0.
_ftspointer_
This field is provided for the use of the application
program and is not modified by the fts functions. It is
initialized to NULL.
_ftsparent_
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 _ftslevel_, _ftsnumber_, and _ftspointer_
fields are guaranteed to be initialized.
_ftslink_
Upon return from the **fts_children**() function, the _ftslink_
field points to the next structure in the NULL-terminated
linked list of directory members. Otherwise, the contents
of the _ftslink_ field are undefined.
_ftscycle_
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 _ftscycle_ 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 _ftscycle_ field are undefined.
_ftsstatp_
A pointer to [**l**][stat(2)](../man2/stat.2.html) 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 _ftspath_ and _ftsaccpath_
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 _ftspathlen_ field. Any such modifications
should be undone before further calls to **fts_read**() are attempted.
The _ftsname_ field is always null-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 ORing the following values:
**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 nonexistent files:
the _ftsstatp_ field is obtained via [stat(2)](../man2/stat.2.html) with a fallback
to [lstat(2)](../man2/lstat.2.html).
**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: the _ftsstatp_ field is
obtained via [lstat(2)](../man2/lstat.2.html).
**FTS_COMFOLLOW**
This option causes any symbolic link specified as a root
path to be followed immediately, as if via **FTS_LOGICAL**,
regardless of the primary mode.
**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. This 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 _ftsstatp_ field) for each
file visited. This option relaxes that requirement as a
performance optimization, allowing the fts functions to set
the _ftsinfo_ field to **FTS_NSOK** and leave the contents of
the _ftsstatp_ field undefined.
**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 _ftsaccpath_, _ftspath_, and _ftspathlen_ fields of
the _FTSENT_ structures may _never_ be used in this comparison. If
the _ftsinfo_ field is set to **FTS_NS** or **FTS_NSOK**, the _ftsstatp_
field may not either. If the **compar**() argument is NULL, the
directory traversal order is in the order listed in _pathargv_ 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 preorder and once in postorder. 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 _[errno](../man3/errno.3.html)_ to 0. If an error unrelated to a file
in the hierarchy occurs, **fts_read**() returns NULL and sets _[errno](../man3/errno.3.html)_ to
indicate the error. If an error related to a returned file
occurs, a pointer to an _FTSENT_ structure is returned, and _[errno](../man3/errno.3.html)_
may or may not have been set (see _ftsinfo_).
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
postorder.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 ftslink field of the FTSENT structure, and is ordered by the user-specified comparison function, if any. Repeated calls to fts_children() will re-create 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 preorder, or the directory does not contain any
files, **fts_children**() returns NULL and sets _[errno](../man3/errno.3.html)_ to zero. If an
error occurs, **fts_children**() returns NULL and sets _[errno](../man3/errno.3.html)_ to
indicate the error.
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.
The _instr_ argument is either zero or 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 _ftsname_ and
_ftsnamelen_ 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.
The _instr_ argument is either 0 (meaning "do nothing") or one of
the following values:
**FTS_AGAIN**
Revisit the file; any file type may be revisited. The next
call to **fts_read**() will return the referenced file. The
_ftsstat_ and _ftsinfo_ 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
postorder directory visits, where it causes the directory
to be revisited (in both preorder and postorder) 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 _ftsinfo_ and _ftsstatp_ 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 _ftsinfo_ and
_ftsstatp_ 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
_ftsinfo_ field will be set to **FTS_SLNONE**.
If the target of the link is a directory, the preorder
return, followed by the return of all of its descendants,
followed by a postorder 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 the file hierarchy stream referred to by 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.
ERRORS top
The function **fts_open**() may fail and set _[errno](../man3/errno.3.html)_ for any of the
errors specified for [open(2)](../man2/open.2.html) and [malloc(3)](../man3/malloc.3.html).
In addition, **fts_open**() may fail and set _[errno](../man3/errno.3.html)_ as follows:
**ENOENT** Any element of _pathargv_ was an empty string.
The function **fts_close**() may fail and set _[errno](../man3/errno.3.html)_ for any of the
errors specified for [chdir(2)](../man2/chdir.2.html) and [close(2)](../man2/close.2.html).
The functions **fts_read**() and **fts_children**() may fail and set _[errno](../man3/errno.3.html)_
for any of the errors specified for [chdir(2)](../man2/chdir.2.html), [malloc(3)](../man3/malloc.3.html),
[opendir(3)](../man3/opendir.3.html), [readdir(3)](../man3/readdir.3.html), and [**l**][stat(2)](../man2/stat.2.html).
In addition, **fts_children**(), **fts_open**(), and **fts_set**() may fail
and set _[errno](../man3/errno.3.html)_ as follows:
**EINVAL** _options_ or _instr_ was invalid.ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌────────────────────────────────────┬───────────────┬───────────┐
│ **Interface** │ **Attribute** │ **Value** │
├────────────────────────────────────┼───────────────┼───────────┤
│ **fts_open**(), **fts_set**(), **fts_close**() │ Thread safety │ MT-Safe │
├────────────────────────────────────┼───────────────┼───────────┤
│ **fts_read**(), **fts_children**() │ Thread safety │ MT-Unsafe │
└────────────────────────────────────┴───────────────┴───────────┘STANDARDS top
None.HISTORY top
glibc 2. 4.4BSD.BUGS top
Before glibc 2.23, all of the APIs described in this man page are
not safe when compiling a program using the LFS APIs (e.g., when
compiling with _-DFILEOFFSETBITS=64_).SEE ALSO top
[find(1)](../man1/find.1.html), [chdir(2)](../man2/chdir.2.html), [lstat(2)](../man2/lstat.2.html), [stat(2)](../man2/stat.2.html), [ftw(3)](../man3/ftw.3.html), [qsort(3)](../man3/qsort.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-12-13 fts(3)
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