xref: /dragonfly/lib/libc/gen/fts.3 (revision 2038fb68)
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28.\"     @(#)fts.3	8.5 (Berkeley) 4/16/94
29.\" $FreeBSD: src/lib/libc/gen/fts.3,v 1.24 2008/01/26 17:09:40 yar Exp $
30.\" $DragonFly: src/lib/libc/gen/fts.3,v 1.4 2007/07/30 22:11:32 swildner Exp $
31.\"
32.Dd January 26, 2008
33.Dt FTS 3
34.Os
35.Sh NAME
36.Nm fts
37.Nd traverse a file hierarchy
38.Sh LIBRARY
39.Lb libc
40.Sh SYNOPSIS
41.In sys/types.h
42.In sys/stat.h
43.In fts.h
44.Ft FTS *
45.Fn fts_open "char * const *path_argv" "int options" "int (*compar)(const FTSENT * const *, const FTSENT * const *)"
46.Ft FTSENT *
47.Fn fts_read "FTS *ftsp"
48.Ft FTSENT *
49.Fn fts_children "FTS *ftsp" "int options"
50.Ft int
51.Fn fts_set "FTS *ftsp" "FTSENT *f" "int options"
52.Ft void
53.Fn fts_set_clientptr "FTS *ftsp" "void *clientdata"
54.Ft void *
55.Fn fts_get_clientptr "FTS *ftsp"
56.Ft FTS *
57.Fn fts_get_stream "FTSENT *f"
58.Ft int
59.Fn fts_close "FTS *ftsp"
60.Sh DESCRIPTION
61The
62.Nm
63functions are provided for traversing
64.Ux
65file hierarchies.
66A simple overview is that the
67.Fn fts_open
68function returns a
69.Dq handle
70on a file hierarchy, which is then supplied to
71the other
72.Nm
73functions.
74The function
75.Fn fts_read
76returns a pointer to a structure describing one of the files in the file
77hierarchy.
78The function
79.Fn fts_children
80returns a pointer to a linked list of structures, each of which describes
81one of the files contained in a directory in the hierarchy.
82In general, directories are visited two distinguishable times; in pre-order
83(before any of their descendants are visited) and in post-order (after all
84of their descendants have been visited).
85Files are visited once.
86It is possible to walk the hierarchy
87.Dq logically
88(ignoring symbolic links)
89or physically (visiting symbolic links), order the walk of the hierarchy or
90prune and/or re-visit portions of the hierarchy.
91.Pp
92Two structures are defined (and typedef'd) in the include file
93.In fts.h .
94The first is
95.Vt FTS ,
96the structure that represents the file hierarchy itself.
97The second is
98.Vt FTSENT ,
99the structure that represents a file in the file
100hierarchy.
101Normally, an
102.Vt FTSENT
103structure is returned for every file in the file
104hierarchy.
105In this manual page,
106.Dq file
107and
108.Dq Vt FTSENT No structure
109are generally
110interchangeable.
111.Pp
112The
113.Vt FTS
114structure contains space for a single pointer, which may be used to
115store application data or per-hierarchy state.
116The
117.Fn fts_set_clientptr
118and
119.Fn fts_get_clientptr
120functions may be used to set and retrieve this pointer.
121This is likely to be useful only when accessed from the sort
122comparison function, which can determine the original
123.Vt FTS
124stream of its arguments using the
125.Fn fts_get_stream
126function.
127The two
128.Li get
129functions are also available as macros of the same name.
130.Pp
131The
132.Vt FTSENT
133structure contains at least the following fields, which are
134described in greater detail below:
135.Bd -literal
136typedef struct _ftsent {
137	int fts_info;			/* status for FTSENT structure */
138	char *fts_accpath;		/* access path */
139	char *fts_path;			/* root path */
140	size_t fts_pathlen;		/* strlen(fts_path) */
141	char *fts_name;			/* file name */
142	size_t fts_namelen;		/* strlen(fts_name) */
143	long fts_level;			/* depth (\-1 to N) */
144	int fts_errno;			/* file errno */
145	long long fts_number;		/* local numeric value */
146	void *fts_pointer;		/* local address value */
147	struct ftsent *fts_parent;	/* parent directory */
148	struct ftsent *fts_link;	/* next file structure */
149	struct ftsent *fts_cycle;	/* cycle structure */
150	struct stat *fts_statp;		/* stat(2) information */
151} FTSENT;
152.Ed
153.Pp
154These fields are defined as follows:
155.Bl -tag -width "fts_namelen"
156.It Fa fts_info
157One of the following values describing the returned
158.Vt FTSENT
159structure and
160the file it represents.
161With the exception of directories without errors
162.Pq Dv FTS_D ,
163all of these
164entries are terminal, that is, they will not be revisited, nor will any
165of their descendants be visited.
166.Bl  -tag -width FTS_DEFAULT
167.It Dv FTS_D
168A directory being visited in pre-order.
169.It Dv FTS_DC
170A directory that causes a cycle in the tree.
171(The
172.Fa fts_cycle
173field of the
174.Vt FTSENT
175structure will be filled in as well.)
176.It Dv FTS_DEFAULT
177Any
178.Vt FTSENT
179structure that represents a file type not explicitly described
180by one of the other
181.Fa fts_info
182values.
183.It Dv FTS_DNR
184A directory which cannot be read.
185This is an error return, and the
186.Fa fts_errno
187field will be set to indicate what caused the error.
188.It Dv FTS_DOT
189A file named
190.Ql .\&
191or
192.Ql ..\&
193which was not specified as a file name to
194.Fn fts_open
195(see
196.Dv FTS_SEEDOT ) .
197.It Dv FTS_DP
198A directory being visited in post-order.
199The contents of the
200.Vt FTSENT
201structure will be unchanged from when
202it was returned in pre-order, i.e., with the
203.Fa fts_info
204field set to
205.Dv FTS_D .
206.It Dv FTS_ERR
207This is an error return, and the
208.Fa fts_errno
209field will be set to indicate what caused the error.
210.It Dv FTS_F
211A regular file.
212.It Dv FTS_NS
213A file for which no
214.Xr stat 2
215information was available.
216The contents of the
217.Fa fts_statp
218field are undefined.
219This is an error return, and the
220.Fa fts_errno
221field will be set to indicate what caused the error.
222.It Dv FTS_NSOK
223A file for which no
224.Xr stat 2
225information was requested.
226The contents of the
227.Fa fts_statp
228field are undefined.
229.It Dv FTS_SL
230A symbolic link.
231.It Dv FTS_SLNONE
232A symbolic link with a non-existent target.
233The contents of the
234.Fa fts_statp
235field reference the file characteristic information for the symbolic link
236itself.
237.El
238.It Fa fts_accpath
239A path for accessing the file from the current directory.
240.It Fa fts_path
241The path for the file relative to the root of the traversal.
242This path contains the path specified to
243.Fn fts_open
244as a prefix.
245.It Fa fts_pathlen
246The length of the string referenced by
247.Fa fts_path .
248.It Fa fts_name
249The name of the file.
250.It Fa fts_namelen
251The length of the string referenced by
252.Fa fts_name .
253.It Fa fts_level
254The depth of the traversal, numbered from \-1 to N, where this file
255was found.
256The
257.Vt FTSENT
258structure representing the parent of the starting point (or root)
259of the traversal is numbered
260.Dv FTS_ROOTPARENTLEVEL
261(\-1), and the
262.Vt FTSENT
263structure for the root
264itself is numbered
265.Dv FTS_ROOTLEVEL
266(0).
267.It Fa fts_errno
268Upon return of a
269.Vt FTSENT
270structure from the
271.Fn fts_children
272or
273.Fn fts_read
274functions, with its
275.Fa fts_info
276field set to
277.Dv FTS_DNR ,
278.Dv FTS_ERR
279or
280.Dv FTS_NS ,
281the
282.Fa fts_errno
283field contains the value of the external variable
284.Va errno
285specifying the cause of the error.
286Otherwise, the contents of the
287.Fa fts_errno
288field are undefined.
289.It Fa fts_number
290This field is provided for the use of the application program and is
291not modified by the
292.Nm
293functions.
294It is initialized to 0.
295.It Fa fts_pointer
296This field is provided for the use of the application program and is
297not modified by the
298.Nm
299functions.
300It is initialized to
301.Dv NULL .
302.It Fa fts_parent
303A pointer to the
304.Vt FTSENT
305structure referencing the file in the hierarchy
306immediately above the current file, i.e., the directory of which this
307file is a member.
308A parent structure for the initial entry point is provided as well,
309however, only the
310.Fa fts_level ,
311.Fa fts_bignum ,
312.Fa fts_number
313and
314.Fa fts_pointer
315fields are guaranteed to be initialized.
316.It Fa fts_link
317Upon return from the
318.Fn fts_children
319function, the
320.Fa fts_link
321field points to the next structure in the NULL-terminated linked list of
322directory members.
323Otherwise, the contents of the
324.Fa fts_link
325field are undefined.
326.It Fa fts_cycle
327If a directory causes a cycle in the hierarchy (see
328.Dv FTS_DC ) ,
329either because
330of a hard link between two directories, or a symbolic link pointing to a
331directory, the
332.Fa fts_cycle
333field of the structure will point to the
334.Vt FTSENT
335structure in the hierarchy that references the same file as the current
336.Vt FTSENT
337structure.
338Otherwise, the contents of the
339.Fa fts_cycle
340field are undefined.
341.It Fa fts_statp
342A pointer to
343.Xr stat 2
344information for the file.
345.El
346.Pp
347A single buffer is used for all of the paths of all of the files in the
348file hierarchy.
349Therefore, the
350.Fa fts_path
351and
352.Fa fts_accpath
353fields are guaranteed to be
354.Dv NUL Ns -terminated
355.Em only
356for the file most recently returned by
357.Fn fts_read .
358To use these fields to reference any files represented by other
359.Vt FTSENT
360structures will require that the path buffer be modified using the
361information contained in that
362.Vt FTSENT
363structure's
364.Fa fts_pathlen
365field.
366Any such modifications should be undone before further calls to
367.Fn fts_read
368are attempted.
369The
370.Fa fts_name
371field is always
372.Dv NUL Ns -terminated .
373.Pp
374Note that the use of
375.Fa fts_bignum
376is mutually exclusive with the use of
377.Fa fts_number
378or
379.Fa fts_pointer .
380.Sh FTS_OPEN
381The
382.Fn fts_open
383function takes a pointer to an array of character pointers naming one
384or more paths which make up a logical file hierarchy to be traversed.
385The array must be terminated by a
386.Dv NULL
387pointer.
388.Pp
389There are
390a number of options, at least one of which (either
391.Dv FTS_LOGICAL
392or
393.Dv FTS_PHYSICAL )
394must be specified.
395The options are selected by
396.Em or Ns 'ing
397the following values:
398.Bl -tag -width "FTS_PHYSICAL"
399.It Dv FTS_COMFOLLOW
400This option causes any symbolic link specified as a root path to be
401followed immediately whether or not
402.Dv FTS_LOGICAL
403is also specified.
404.It Dv FTS_LOGICAL
405This option causes the
406.Nm
407routines to return
408.Vt FTSENT
409structures for the targets of symbolic links
410instead of the symbolic links themselves.
411If this option is set, the only symbolic links for which
412.Vt FTSENT
413structures
414are returned to the application are those referencing non-existent files.
415Either
416.Dv FTS_LOGICAL
417or
418.Dv FTS_PHYSICAL
419.Em must
420be provided to the
421.Fn fts_open
422function.
423.It Dv FTS_NOCHDIR
424As a performance optimization, the
425.Nm
426functions change directories as they walk the file hierarchy.
427This has the side-effect that an application cannot rely on being
428in any particular directory during the traversal.
429The
430.Dv FTS_NOCHDIR
431option turns off this optimization, and the
432.Nm
433functions will not change the current directory.
434Note that applications should not themselves change their current directory
435and try to access files unless
436.Dv FTS_NOCHDIR
437is specified and absolute
438pathnames were provided as arguments to
439.Fn fts_open .
440.It Dv FTS_NOSTAT
441By default, returned
442.Vt FTSENT
443structures reference file characteristic information (the
444.Fa statp
445field) for each file visited.
446This option relaxes that requirement as a performance optimization,
447allowing the
448.Nm
449functions to set the
450.Fa fts_info
451field to
452.Dv FTS_NSOK
453and leave the contents of the
454.Fa statp
455field undefined.
456.It Dv FTS_PHYSICAL
457This option causes the
458.Nm
459routines to return
460.Vt FTSENT
461structures for symbolic links themselves instead
462of the target files they point to.
463If this option is set,
464.Vt FTSENT
465structures for all symbolic links in the
466hierarchy are returned to the application.
467Either
468.Dv FTS_LOGICAL
469or
470.Dv FTS_PHYSICAL
471.Em must
472be provided to the
473.Fn fts_open
474function.
475.It Dv FTS_SEEDOT
476By default, unless they are specified as path arguments to
477.Fn fts_open ,
478any files named
479.Ql .\&
480or
481.Ql ..\&
482encountered in the file hierarchy are ignored.
483This option causes the
484.Nm
485routines to return
486.Vt FTSENT
487structures for them.
488.It Dv FTS_XDEV
489This option prevents
490.Nm
491from descending into directories that have a different device number
492than the file from which the descent began.
493.El
494.Pp
495The argument
496.Fn compar
497specifies a user-defined function which may be used to order the traversal
498of the hierarchy.
499It
500takes two pointers to pointers to
501.Vt FTSENT
502structures as arguments and
503should return a negative value, zero, or a positive value to indicate
504if the file referenced by its first argument comes before, in any order
505with respect to, or after, the file referenced by its second argument.
506The
507.Fa fts_accpath ,
508.Fa fts_path
509and
510.Fa fts_pathlen
511fields of the
512.Vt FTSENT
513structures may
514.Em never
515be used in this comparison.
516If the
517.Fa fts_info
518field is set to
519.Dv FTS_NS
520or
521.Dv FTS_NSOK ,
522the
523.Fa fts_statp
524field may not either.
525If the
526.Fn compar
527argument is
528.Dv NULL ,
529the directory traversal order is in the order listed in
530.Fa path_argv
531for the root paths, and in the order listed in the directory for
532everything else.
533.Sh FTS_READ
534The
535.Fn fts_read
536function returns a pointer to an
537.Vt FTSENT
538structure describing a file in
539the hierarchy.
540Directories (that are readable and do not cause cycles) are visited at
541least twice, once in pre-order and once in post-order.
542All other files are visited at least once.
543(Hard links between directories that do not cause cycles or symbolic
544links to symbolic links may cause files to be visited more than once,
545or directories more than twice.)
546.Pp
547If all the members of the hierarchy have been returned,
548.Fn fts_read
549returns
550.Dv NULL
551and sets the external variable
552.Va errno
553to 0.
554If an error unrelated to a file in the hierarchy occurs,
555.Fn fts_read
556returns
557.Dv NULL
558and sets
559.Va errno
560appropriately.
561If an error related to a returned file occurs, a pointer to an
562.Vt FTSENT
563structure is returned, and
564.Va errno
565may or may not have been set (see
566.Fa fts_info ) .
567.Pp
568The
569.Vt FTSENT
570structures returned by
571.Fn fts_read
572may be overwritten after a call to
573.Fn fts_close
574on the same file hierarchy stream, or, after a call to
575.Fn fts_read
576on the same file hierarchy stream unless they represent a file of type
577directory, in which case they will not be overwritten until after a call to
578.Fn fts_read
579after the
580.Vt FTSENT
581structure has been returned by the function
582.Fn fts_read
583in post-order.
584.Sh FTS_CHILDREN
585The
586.Fn fts_children
587function returns a pointer to an
588.Vt FTSENT
589structure describing the first entry in a NULL-terminated linked list of
590the files in the directory represented by the
591.Vt FTSENT
592structure most recently returned by
593.Fn fts_read .
594The list is linked through the
595.Fa fts_link
596field of the
597.Vt FTSENT
598structure, and is ordered by the user-specified comparison function, if any.
599Repeated calls to
600.Fn fts_children
601will recreate this linked list.
602.Pp
603As a special case, if
604.Fn fts_read
605has not yet been called for a hierarchy,
606.Fn fts_children
607will return a pointer to the files in the logical directory specified to
608.Fn fts_open ,
609i.e., the arguments specified to
610.Fn fts_open .
611Otherwise, if the
612.Vt FTSENT
613structure most recently returned by
614.Fn fts_read
615is not a directory being visited in pre-order,
616or the directory does not contain any files,
617.Fn fts_children
618returns
619.Dv NULL
620and sets
621.Va errno
622to zero.
623If an error occurs,
624.Fn fts_children
625returns
626.Dv NULL
627and sets
628.Va errno
629appropriately.
630.Pp
631The
632.Vt FTSENT
633structures returned by
634.Fn fts_children
635may be overwritten after a call to
636.Fn fts_children ,
637.Fn fts_close
638or
639.Fn fts_read
640on the same file hierarchy stream.
641.Pp
642.Em Option
643may be set to the following value:
644.Bl -tag -width FTS_NAMEONLY
645.It Dv FTS_NAMEONLY
646Only the names of the files are needed.
647The contents of all the fields in the returned linked list of structures
648are undefined with the exception of the
649.Fa fts_name
650and
651.Fa fts_namelen
652fields.
653.El
654.Sh FTS_SET
655The function
656.Fn fts_set
657allows the user application to determine further processing for the
658file
659.Fa f
660of the stream
661.Fa ftsp .
662The
663.Fn fts_set
664function
665returns 0 on success, and \-1 if an error occurs.
666.Em Option
667must be set to one of the following values:
668.Bl -tag -width FTS_PHYSICAL
669.It Dv FTS_AGAIN
670Re-visit the file; any file type may be re-visited.
671The next call to
672.Fn fts_read
673will return the referenced file.
674The
675.Fa fts_stat
676and
677.Fa fts_info
678fields of the structure will be reinitialized at that time,
679but no other fields will have been changed.
680This option is meaningful only for the most recently returned
681file from
682.Fn fts_read .
683Normal use is for post-order directory visits, where it causes the
684directory to be re-visited (in both pre and post-order) as well as all
685of its descendants.
686.It Dv FTS_FOLLOW
687The referenced file must be a symbolic link.
688If the referenced file is the one most recently returned by
689.Fn fts_read ,
690the next call to
691.Fn fts_read
692returns the file with the
693.Fa fts_info
694and
695.Fa fts_statp
696fields reinitialized to reflect the target of the symbolic link instead
697of the symbolic link itself.
698If the file is one of those most recently returned by
699.Fn fts_children ,
700the
701.Fa fts_info
702and
703.Fa fts_statp
704fields of the structure, when returned by
705.Fn fts_read ,
706will reflect the target of the symbolic link instead of the symbolic link
707itself.
708In either case, if the target of the symbolic link does not exist the
709fields of the returned structure will be unchanged and the
710.Fa fts_info
711field will be set to
712.Dv FTS_SLNONE .
713.Pp
714If the target of the link is a directory, the pre-order return, followed
715by the return of all of its descendants, followed by a post-order return,
716is done.
717.It Dv FTS_SKIP
718No descendants of this file are visited.
719The file may be one of those most recently returned by either
720.Fn fts_children
721or
722.Fn fts_read .
723.El
724.Sh FTS_CLOSE
725The
726.Fn fts_close
727function closes a file hierarchy stream
728.Fa ftsp
729and restores the current directory to the directory from which
730.Fn fts_open
731was called to open
732.Fa ftsp .
733The
734.Fn fts_close
735function
736returns 0 on success, and \-1 if an error occurs.
737.Sh ERRORS
738The function
739.Fn fts_open
740may fail and set
741.Va errno
742for any of the errors specified for the library functions
743.Xr open 2
744and
745.Xr malloc 3 .
746.Pp
747The function
748.Fn fts_close
749may fail and set
750.Va errno
751for any of the errors specified for the library functions
752.Xr chdir 2
753and
754.Xr close 2 .
755.Pp
756The functions
757.Fn fts_read
758and
759.Fn fts_children
760may fail and set
761.Va errno
762for any of the errors specified for the library functions
763.Xr chdir 2 ,
764.Xr malloc 3 ,
765.Xr opendir 3 ,
766.Xr readdir 3
767and
768.Xr stat 2 .
769.Pp
770In addition,
771.Fn fts_children ,
772.Fn fts_open
773and
774.Fn fts_set
775may fail and set
776.Va errno
777as follows:
778.Bl -tag -width Er
779.It Bq Er EINVAL
780The options were invalid.
781.El
782.Sh SEE ALSO
783.Xr find 1 ,
784.Xr chdir 2 ,
785.Xr stat 2 ,
786.Xr ftw 3 ,
787.Xr qsort 3
788.Sh HISTORY
789The
790.Nm
791interface was first introduced in
792.Bx 4.4 .
793The
794.Fn fts_get_clientptr ,
795.Fn fts_get_stream ,
796and
797.Fn fts_set_clientptr
798functions were introduced in
799.Fx 5.0 ,
800principally to provide for alternative interfaces to the
801.Nm
802functionality using different data structures.
803