Originální popis anglicky:
fts,
fts_open,
fts_read,
fts_children,
fts_set,
fts_close
—
traverse a file hierarchy
Návod, kniha: Library Functions Manual
#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; /* 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_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() (see
FTS_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 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 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, 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 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(), 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- 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:
- [
EINVAL]
- The options were invalid.
find(1),
chdir(2),
stat(2),
qsort(3)
BSD 4.4. The
fts utility is expected to be included
in a future
IEEE Std 1003.1-1988
(“POSIX.1”) revision.
These functions are available in Linux since glibc2.
