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[unix-history] / usr / src / lib / libc / gen / fts.3

.\" Copyright (c) 1989 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"	@(#)fts.3	5.9 (Berkeley) %G%
.\"
.TH FTS 3 ""
.UC 7
.SH NAME
fts \- traverse a file hierarchy
.SH SYNOPSIS
.nf
.ft B
#include <sys/types.h>
#include <sys/stat.h>
#include <fts.h>

FTS *fts_open(char * const *path_argv, int options,
.ti +5
int *compar(const FTSENT *, const FTSENT *));

FTSENT *
fts_read(FTS *ftsp);

FTSENT *
fts_children(FTS *ftsp);

fts_set(FTS ftsp, FTSENT *f, int options);

fts_close(FTS *ftsp);
.ft R
.fi
.SH DESCRIPTION
The
.IR fts (3)
functions are provided for traversing UNIX file hierarchies.
.PP
The simple overview is that the
.I fts_open
function returns a ``handle'' on a file hierarchy, which is supplied to
the other
.I fts
functions to determine which hierarchy they operate on.
The function
.I fts_read
returns a pointer to a structure describing one of the files in the file
hierarchy.
The function
.I 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.
.PP
Two structures are defined (and typedef'd) in the include file <fts.h>.
The first is FTS, the structure that represents the file hierarchy stream.
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:
.sp
.nf
.ta .5i +.5i +\w'struct ftsent *parent;\0\0\0'u
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) */
	long fts_number;			/* local numeric value */
	void *fts_pointer;		/* local address value */
	struct ftsent *fts_parent;		/* parent directory */
	struct ftsent *fts_link;		/* cycle or next file structure */
	struct stat fts_statb;			/* stat(2) information */
} FTSENT;
.fi
.\" Makes the output look a lot better.
.bp
.PP
These fields are defined as follows:
.TP
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.
.RS
.TP
FTS_D
A directory being visited in pre-order.
.TP
FTS_DC
A directory that causes a cycle in the tree.
(The
.I fts_link
field of the FTSENT structure will be filled in as well.)
.TP
FTS_DEFAULT
Any FTSENT structure that represents a file type not explicitly described
by one of the other
.I fts_info
values.
.TP
FTS_DNR
A directory which cannot be read.
An error return; the external variable
.I errno
will be set to indicate the error.
.TP
FTS_DOT
A file named ``.'' or ``..'' which was not specified as a file name to
.I fts_open
(see FTS_SEEDOT).
.TP
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
.I fts_info
field set to FTS_D.
.TP
FTS_ERR
An error return; the external variable
.I errno
will be set to indicate the error.
.TP
FTS_F
A regular file.
.TP
FTS_NS
A file for which no
.IR stat (2)
information was available.
The contents of the
.I fts_statb
field are undefined.
An error return; the external variable
.I errno
will be set to indicate the error.
.TP
FTS_NSOK
A file for which no
.IR stat (2)
information was requested.
The contents of the
.I fts_statb
field are undefined.
.TP
FTS_SL
A symbolic link.
.TP
FTS_SLNONE
A symbolic link with a non-existent target.
The contents of the
.I fts_statb
field contain the file characteristic information for the symbolic link
itself.
.RE
.TP
fts_accpath
A path for accessing the file from the current directory.
.TP
fts_path
The path for the file relative to the root of the traversal.
This path contains the path specified to
.I fts_open
as a prefix.
.TP
fts_pathlen
The length of the string referenced by
.IR fts_path .
.TP
fts_name
The name of the file.
.TP
fts_namelen
The length of the string referenced by
.IR fts_name .
.TP
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.
.TP
fts_number
This field is provided for the use of the application program and is
not modified by the
.I fts
functions.
It is initialized to 0.
The fields
.I fts_number
and
.I fts_pointer
occupy the same physical location; using both may cause undefined results.
.TP
fts_pointer
This field is provided for the use of the application program and is
not modified by the
.I fts
functions.
It is initialized to NULL.
The fields
.I fts_number
and
.I fts_pointer
occupy the same physical location; using both may cause undefined results.
.TP
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
.IR fts_level ,
.I fts_number
and
.I fts_pointer
fields are guaranteed to be initialized.
.TP
fts_link
The
.I fts_link
field has two separate uses.
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
.I fts_link
field of the structure will point to the FTSENT structure in the hierarchy
that references the same file as the current FTSENT structure.
Also, upon return from the
.I fts_children
function, the
.I fts_link
field points to the next structure in the linked list of directory members.
Otherwise, the contents of the
.I fts_link
field are undefined.
.TP
fts_statb
.IR Stat (2)
information for the file.
.SH FTS_OPEN
The
.I 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.
.PP
.I Fts_open
has a number of options, at least one of which (either FTS_LOGICAL or
FTS_PHYSICAL) must be specified.
The options are selected by
.IR or 'ing
the following values:
.TP
FTS_LOGICAL
This option causes the
.I 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
.B must
be provided to the
.I fts_open
function.
.TP
FTS_NOCHDIR
As a performance optimization, the
.I 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
.I 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
.IR fts_open .
.TP
FTS_NOSTAT
By default, returned FTSENT structures contain file characteristic
information (the
.I statb
field) for each file visited.
This option relaxes that requirement as a performance optimization,
allowing the
.I fts
functions to set the
.I fts_info
field to FTS_NSOK and leave the contents of the
.I statb
field undefined.
.TP
FTS_PHYSICAL
This option causes the
.I 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
.B must
be provided to the
.I fts_open
function.
.TP
FTS_SEEDOT
By default, unless they are specified as path arguments to
.IR fts_open ,
any files named ``.'' and ``..'' encountered in the file hierarchy are
ignored.
This option causes the
.I fts
routines to return FTSENT structures for them.
.TP
FTS_XDEV
This option prevents
.I fts
from descending into directories that have a different device number
than the file from which the descent began.
.PP
The argument
.I compar
specifies a user-defined function which may be used to order the traversal
of the hierarchy.
.I Compar
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
.IR fts_accpath ,
.I fts_path
and
.I fts_pathlen
fields of the FTSENT structures may
.B never
be used in this comparison.
If the 
.I fts_info
field is set to FTS_NS or FTS_NSOK, the
.I fts_stab
field may not either.
If the
.I compar
argument is NULL, the directory traversal order is unspecified except
for the root paths which are traversed in the order listed in
.IR path_argv .
.SH FTS_READ
The
.I 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.)
.PP
If all the members of the hierarchy have been returned,
.I fts_read
returns NULL and sets the external variable
.I errno
to 0.
If an error unrelated to a file in the hierarchy occurs,
.I fts_read
returns NULL and sets
.I errno
appropriately.
If an error related to a returned file occurs, a pointer to an FTSENT
structure is returned, and
.I errno
may or may not have been set (see
.IR fts_info ).
.PP
The FTSENT structures returned by
.I fts_read
may be overwritten after a call to
.I fts_close
on the same file hierarchy stream, or, after a call to
.I 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
.I fts_read
after the FTSENT structure has been returned by the function
.I fts_read
in post-order.
.SH FTS_CHILDREN
The
.I fts_children
function returns a pointer to an FTSENT structure describing the first
entry in a linked list of the files in the directory represented by the
FTSENT structure most recently returned by
.IR fts_read .
The list is linked through the
.I fts_link
field of the FTSENT structure, and is ordered by the user-specified
comparison function, if any.
Repeated calls to
.I fts_children
will recreate this linked list.
.PP
If the FTSENT structure most recently returned by
.I fts_read
is not a directory being visited in pre-order,
or the directory does not contain any files,
.I fts_children
returns NULL and sets
.I errno
to zero.
If an error occurs,
.I fts_children
returns NULL and sets
.I errno
appropriately.
.PP
The FTSENT structures returned by
.I fts_children
may be overwritten after a call to
.I fts_close
on the same file hierarchy stream, or after a call to
.I fts_children
or
.I fts_read
on the same file hierarchy stream.
.PP
A single buffer is used for all of the paths of all of the files in the
file hierarchy.
Therefore, the
.I fts_path
and
.I fts_accpath
fields are guaranteed to be NULL-terminated
.B only
for the file most recently returned by
.IR 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
.I fts_pathlen
field.
Any such modifications should be undone before further calls to
.I fts_read
are attempted.
The
.I fts_name
field is always NULL-terminated.
.SH FTS_SET
The function
.I fts_set
allows the user application to determine further processing for the
file
.I f
of the stream
.IR ftsp .
.I Fts_set
returns 0 on success, and -1 if an error occurs.
.I Option
must be set to one of the following values:
.TP
FTS_AGAIN
Re-visit the file; any file type may be re-visited.
The next call to
.I fts_read
will return the referenced file.
The
.I fts_stat
and
.I 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
.IR 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.
.TP
FTS_FOLLOW
The referenced file must be a symbolic link.
If the referenced file is the one most recently returned by
.IR fts_read ,
the next call to
.I fts_read
returns the file with the
.I fts_info
and
.I fts_statb
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
.IR fts_children ,
the
.I fts_info
and
.I fts_statb
fields of the structure, when returned by
.IR 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
.I 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.
.TP
FTS_SKIP
No descendants of this file are visited.
The file may be one of those most recently returned by either
.I fts_children
or
.IR fts_read .
.SH FTS_CLOSE
The
.I fts_close
function closes a file hierarchy stream
.I ftsp
and restores the current directory to the directory from which
.I fts_open
was called to open
.IR ftsp .
.I Fts_close
returns 0 on success, and -1 if an error occurs.
.SH ERRORS
.I Fts_open
may fail and set errno for any of the errors specified for the library
functions
.IR open (2)
and
.IR malloc (3).
.PP
.I Fts_close
may fail and set errno for any of the errors specified for the library
functions
.IR chdir (2)
and
.IR close (2).
.PP
.I Fts_read
and
.I fts_children
may fail and set errno for any of the errors specified for the library
functions
.IR chdir (2),
.IR malloc (3),
.IR opendir (3),
.IR readdir (3)
and
.IR stat (2).
.SH SEE ALSO
find(1), chdir(2), stat(2), qsort(3)
.SH STANDARDS
The
.I fts
utility is expected to be a superset of the IEEE Std 1003.1 (``POSIX'')
specification.