FTS(3C) | Standard C Library Functions | FTS(3C) |
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 option);
int
fts_close
(FTS
*ftsp);
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:
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
FTS_DC
FTSENT
structure will be filled in as
well.)FTS_DEFAULT
FTSENT
structure that represents a file
type not explicitly described by one of the other
fts_info values.FTS_DNR
FTS_DOT
fts_open
()
(see FTS_SEEDOT
).FTS_DP
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
FTS_F
FTS_NS
FTS_NSOK
FTS_SL
FTS_SLNONE
fts_open
() as a
prefix.FTSENT
structure representing the
parent of the starting point (or root) of the traversal is numbered
FTS_ROOTPARENTLEVEL
(-1), and the
FTSENT
structure for the root itself is numbered
FTS_ROOTLEVEL
(0). Note that while
fts_level cannot hold a number of levels greater
than FTS_MAXLEVEL
, the fts
functions themselves are not limited to a fixed number of levels.
Application code that inspects fts_level should be
written with this in mind.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
functions. It is initialized
to 0.fts
functions. It is initialized
to NULL
.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_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.
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
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
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
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_XDEV
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.
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 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
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
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
().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.
The fts routines provide no locking. While the
fts_open
() function is
Safe and
can be called from multiple threads simultaneously, the individual handles
returned from the fts_open
() function are not
thread-safe. If callers need to operate on a single
FTS structure, then it is their responsibility to
ensure that none of the other functions are called from multiple threads
simultaneously. This implies that the fts_read
(),
fts_children
(), fts_set
(),
and fts_close
() functions are
Unsafe.
These routines are not Async-Signal-Safe and callers should not assume that the implementation of these functions will be Fork-Safe. If callers implement their own locking structures around the use of these routines, they must ensure that those locks are accounted for when forking by the use of routines such as pthread_atfork(3C).
The function fts_open
() may fail and set
errno for any of the errors specified for the library
functions open(2) and
malloc(3C).
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(3C),
opendir(3C),
readdir(3C) and
stat(2).
In addition, fts_children
(),
fts_open
() and fts_set
() may
fail and set errno as follows:
EINVAL
See Locking.
March 28, 2017 | OmniOS |