Index of Section 3 Manual Pages
| Interix / SUA | fts_set.3 | Interix / SUA |
fts_set(3) fts_set(3)
fts_open()
NAME
fts_open(), fts_read(), fts_children(), fts_set(), fts_close() - traverse
a file hierarchy
SYNOPSIS
#include
#include
#include
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)
DESCRIPTION
The fts(3) functions are provided for traversing file hierarchies. A
simple overview is that the fts_open(3) function returns a handle on a
file hierarchy, which is then supplied to the other fts(3) functions. The
function fts_read(3) returns a pointer to a structure describing one of
the files in the file hierarchy. The function fts_children(3) 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 or physically, 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 .
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() 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(3) (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(3) 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(3) or
fts_read(3) 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(3) 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(3) 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(3) 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(3). 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(3) are attempted. The fts_name field is always NULL -terminated.
FTS_OPEN
The fts_open(3) 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(3) 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(3) function.
FTS_NOCHDIR
As a performance optimization, the fts(3) 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(3) 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(3).
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(3) 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(3) 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(3) function.
FTS_SEEDOT
By default, unless they are specified as path arguments to
fts_open(3), any files named . or .. encountered in the file hierarchy
are ignored. This option causes the fts(3) routines to return FTSENT
structures for them.
FTS_XDEV
This option prevents fts(3) 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
The fts_read(3) 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(3)
returns NULL and sets the external variable errno to 0. If an error
unrelated to a file in the hierarchy occurs, fts_read(3) 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(3) may be overwritten after a
call to fts_close(3) on the same file hierarchy stream, or, after a call
to fts_read(3) 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(3) after the FTSENT structure has been returned
by the function fts_read(3) in post-order.
FTS_CHILDREN
The fts_children(3) 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(3). 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(3) will recreate this
linked list.
As a special case, if fts_read(3) has not yet been called for a hierarchy,
fts_children(3) will return a pointer to the files in the logical
directory specified to fts_open(3), i.e. the arguments specified to
fts_open(3). Otherwise, if the FTSENT structure most recently returned by
fts_read(3) is not a directory being visited in pre-order, or the
directory does not contain any files, fts_children(3) returns NULL and
sets errno to zero. If an error occurs, fts_children(3) returns NULL and
sets errno appropriately.
The FTSENT structures returned by fts_children(3) may be overwritten after
a call to fts_children(3), fts_close(3) or fts_read(3) 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.
FTS_SET
The function fts_set(3) allows the user application to determine further
processing for the file f of the stream ftsp. The fts_set(3) 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 revisited. The next call to
fts_read(3) 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(3). 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(3), the next call to
fts_read(3) 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(3), the fts_info and fts_statp fields of the
structure, when returned by fts_read(3), 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(3) or fts_read(3).
FTS_CLOSE
The fts_close(3) function closes a file hierarchy stream ftsp and restores
the current directory to the directory from which fts_open(3) was called
to open ftsp. The fts_close(3) function returns 0 on success, and -1 if an
error occurs.
ERRORS
The function fts_open(3) may fail and set errno for any of the errors
specified for the library functions open(2) and malloc(3).
The function fts_close(3) may fail and set errno for any of the errors
specified for the library functions chdir(2) and close(2).
The functions fts_read(3) and fts_children(3) may fail and set errno for
any of the errors specified for the library functions chdir(2), malloc(3),
opendir(3), readdir(2) and stat(2).
In addition, fts_children(3), fts_open(3) and fts_set(3) may fail and set
errno as follows:
[EINVAL]
The options were invalid.
SEE ALSO
find(1)
chdir(2)
stat(2)
qsort(3)
USAGE NOTES
None of these functions are thread safe.
None of these functions are async-signal safe.