fts_read.3.gz
FTS
NAME
SYNOPSIS
DESCRIPTION
The
functions are provided for traversing
file hierarchies.
A simple overview is that the
function returns a ``handle'' on a file hierarchy, which is then supplied to
the other
functions.
The function
returns a pointer to a structure describing one of the files in the file
hierarchy.
The function
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
The first is
the structure that represents the file hierarchy itself.
The second is
the structure that represents a file in the file
hierarchy.
Normally, an
structure is returned for every file in the file
hierarchy.
In this manual page, ``file'' and
are generally
interchangeable.
The
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; /* 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; /* stat(2) information */
} FTSENT;
These fields are defined as follows:
- fts_info One of the following flags describing the returned structure and the file it represents. With the exception of directories without errors
all of these
entries are terminal, that is, they will not be revisited, nor will any
of their descendants be visited.
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
as a prefix.
fts_pathlen
The length of the string referenced by
fts_name
The name of the file.
fts_namelen
The length of the string referenced by
fts_level
The depth of the traversal, numbered from -1 to N, where this file
was found.
The
structure representing the parent of the starting point (or root)
of the traversal is numbered -1, and the
structure for the root
itself is numbered 0.
fts_errno
Upon return of a
structure from the
or
functions, with its
field set to
or
the
field contains the value of the external variable
specifying the cause of the error.
Otherwise, the contents of the
field are undefined.
fts_number
This field is provided for the use of the application program and is
not modified by the
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
functions.
It is initialized to
fts_parent
A pointer to the
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
and
fields are guaranteed to be initialized.
fts_link
Upon return from the
function, the
field points to the next structure in the NULL-terminated linked list of
directory members.
Otherwise, the contents of the
field are undefined.
fts_cycle
If a directory causes a cycle in the hierarchy (see
either because
of a hard link between two directories, or a symbolic link pointing to a
directory, the
field of the structure will point to the
structure in the hierarchy that references the same file as the current
structure.
Otherwise, the contents of the
field are undefined.
fts_statp
A pointer to
stat(2)
information for the file.
- FTS_D A directory being visited in pre-order.
- FTS_DC A directory that causes a cycle in the tree. (The field of the structure will be filled in as well.)
- FTS_DEFAULT Any structure that represents a file type not explicitly described by one of the other values.
- FTS_DNR A directory which cannot be read. This is an error return, and the field will be set to indicate what caused the error.
- FTS_DOT A file named or which was not specified as a filename to (see
- FTS_DP A directory being visited in post-order. The contents of the structure will be unchanged from when it was returned in pre-order, that is, with the field set to
- FTS_ERR This is an error return, and the 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 field are undefined. This is an error return, and the 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 field are undefined.
- FTS_SL A symbolic link.
- FTS_SLNONE A symbolic link with a non-existent target. The contents of the field reference the file characteristic information for the symbolic link itself.
A single buffer is used for all of the paths of all of the files in the
file hierarchy.
Therefore, the
and
fields are guaranteed to be
for the file most recently returned by
To use these fields to reference any files represented by other
structures will require that the path buffer be modified using the
information contained in that
structure's
field.
Any such modifications should be undone before further calls to
are attempted.
The
field is always
FTS_OPEN
The
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
pointer.
There are
a number of options, at least one of which (either
or
must be specified.
The options are selected by
the following values:
- FTS_COMFOLLOW This option causes any symbolic link specified as a root path to be followed immediately whether or not is also specified.
- FTS_LOGICAL This option causes the routines to return structures for the targets of symbolic links instead of the symbolic links themselves. If this option is set, the only symbolic links for which structures are returned to the application are those referencing non-existent files. Either or be provided to the function.
- FTS_NOCHDIR As a performance optimization, the 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 option turns off this optimization, and the functions will not change the current directory. Note that applications should not themselves change their current directory and try to access files unless is specified and absolute pathnames were provided as arguments to
- FTS_NOSTAT By default, returned structures reference file characteristic information (the field) for each file visited. This option relaxes that requirement as a performance optimization, allowing the functions to set the field to and leave the contents of the field undefined.
- FTS_PHYSICAL This option causes the routines to return structures for symbolic links themselves instead of the target files they point to. If this option is set, structures for all symbolic links in the hierarchy are returned to the application. Either or be provided to the function.
- FTS_SEEDOT By default, unless they are specified as path arguments to any files named or encountered in the file hierarchy are ignored. This option causes the routines to return structures for them.
- FTS_XDEV This option prevents from descending into directories that have a different device number than the file from which the descent began.
The argument
specifies a user-defined function which may be used to order the traversal
of the hierarchy.
It
takes two pointers to pointers to
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
and
fields of the
structures may
be used in this comparison.
If the
field is set to
or
the
field may not either.
If the
argument is
the directory traversal order is in the order listed in
for the root paths, and in the order listed in the directory for
everything else.
FTS_READ
The
function returns a pointer to an
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,
returns
and sets the external variable
to 0.
If an error unrelated to a file in the hierarchy occurs,
returns
and sets
appropriately.
If an error related to a returned file occurs, a pointer to an
structure is returned, and
may or may not have been set (see
The
structures returned by
may be overwritten after a call to
on the same file hierarchy stream, or, after a call to
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
after the
structure has been returned by the function
in post-order.
FTS_CHILDREN
The
function returns a pointer to an
structure describing the first entry in a NULL-terminated linked list of
the files in the directory represented by the
structure most recently returned by
The list is linked through the
field of the
structure, and is ordered by the user-specified comparison function, if any.
Repeated calls to
will recreate this linked list.
As a special case, if
has not yet been called for a hierarchy,
will return a pointer to the files in the logical directory specified to
that is, the arguments specified to
Otherwise, if the
structure most recently returned by
is not a directory being visited in pre-order,
or the directory does not contain any files,
returns
and sets
to zero.
If an error occurs,
returns
and sets
appropriately.
The
structures returned by
may be overwritten after a call to
or
on the same file hierarchy stream.
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 and fields.
FTS_SET
The function
allows the user application to determine further processing for the
file
of the stream
The
function
returns 0 on success, and -1 if an error occurs.
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 will return the referenced file. The and 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 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 the next call to returns the file with the and 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 the and fields of the structure, when returned by 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 field will be set to
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
or
FTS_CLOSE
The
function closes a file hierarchy stream
and restores the current directory to the directory from which
was called to open
The
function
returns 0 on success, and -1 if an error occurs.
ERRORS
The function
may fail and set
for any of the errors specified for the library functions
open(2)
and
malloc(3)
The function
may fail and set
for any of the errors specified for the library functions
chdir(2)
and
close(2)
The functions
and
may fail and set
for any of the errors specified for the library functions
chdir(2)
malloc(3)
opendir(3)
readdir(3)
and
stat(2)
In addition,
and
may fail and set
as follows:
- EINVAL The options were invalid.
VERSIONS
These functions are available in Linux since glibc2.
CONFORMING TO
4.4BSD.
The
utility is expected to be included in a future
revision.
