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[dragonfly.git] / lib / libc / gen / fts.3
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32.\" @(#)fts.3 8.5 (Berkeley) 4/16/94
33.\" $FreeBSD: src/lib/libc/gen/fts.3,v 1.7.2.6 2003/03/13 18:05:37 trhodes Exp $
44cb301e 34.\" $DragonFly: src/lib/libc/gen/fts.3,v 1.3 2006/05/26 19:39:36 swildner Exp $
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35.\"
36.Dd September 15, 2002
37.Dt FTS 3
38.Os
39.Sh NAME
40.Nm fts
41.Nd traverse a file hierarchy
42.Sh LIBRARY
43.Lb libc
44.Sh SYNOPSIS
45.In sys/types.h
46.In sys/stat.h
47.In fts.h
48.Ft FTS *
49.Fn fts_open "char * const *path_argv" "int options" "int (*compar)(const FTSENT **, const FTSENT **)"
50.Ft FTSENT *
51.Fn fts_read "FTS *ftsp"
52.Ft FTSENT *
53.Fn fts_children "FTS *ftsp" "int options"
54.Ft int
55.Fn fts_set "FTS *ftsp" "FTSENT *f" "int options"
56.Ft int
57.Fn fts_close "FTS *ftsp"
58.Sh DESCRIPTION
59The
60.Nm
61functions are provided for traversing
62.Tn UNIX
63file hierarchies.
64A simple overview is that the
65.Fn fts_open
66function returns a
67.Dq handle
68on a file hierarchy, which is then supplied to
69the other
70.Nm
71functions.
72The function
73.Fn fts_read
74returns a pointer to a structure describing one of the files in the file
75hierarchy.
76The function
77.Fn fts_children
78returns a pointer to a linked list of structures, each of which describes
79one of the files contained in a directory in the hierarchy.
80In general, directories are visited two distinguishable times; in pre-order
81(before any of their descendants are visited) and in post-order (after all
82of their descendants have been visited).
83Files are visited once.
84It is possible to walk the hierarchy
85.Dq logically
86(ignoring symbolic links)
87or physically (visiting symbolic links), order the walk of the hierarchy or
88prune and/or re-visit portions of the hierarchy.
89.Pp
90Two structures are defined (and typedef'd) in the include file
44cb301e 91.In fts.h .
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92The first is
93.Fa FTS ,
94the structure that represents the file hierarchy itself.
95The second is
96.Fa FTSENT ,
97the structure that represents a file in the file
98hierarchy.
99Normally, an
100.Fa FTSENT
101structure is returned for every file in the file
102hierarchy.
103In this manual page,
104.Dq file
105and
106.Dq Fa FTSENT No structure
107are generally
108interchangeable.
109The
110.Fa FTSENT
111structure contains at least the following fields, which are
112described in greater detail below:
113.Bd -literal
114typedef struct _ftsent {
115 u_short fts_info; /* flags for FTSENT structure */
116 char *fts_accpath; /* access path */
117 char *fts_path; /* root path */
118 u_short fts_pathlen; /* strlen(fts_path) */
119 char *fts_name; /* file name */
120 u_short fts_namelen; /* strlen(fts_name) */
121 short fts_level; /* depth (\-1 to N) */
122 int fts_errno; /* file errno */
123 long fts_number; /* local numeric value */
124 void *fts_pointer; /* local address value */
125 struct ftsent *fts_parent; /* parent directory */
126 struct ftsent *fts_link; /* next file structure */
127 struct ftsent *fts_cycle; /* cycle structure */
128 struct stat *fts_statp; /* stat(2) information */
129} FTSENT;
130.Ed
131.Pp
132These fields are defined as follows:
133.Bl -tag -width "fts_namelen"
134.It Fa fts_info
135One of the following values describing the returned
136.Vt FTSENT
137structure and
138the file it represents.
139With the exception of directories without errors
140.Pq Dv FTS_D ,
141all of these
142entries are terminal, that is, they will not be revisited, nor will any
143of their descendants be visited.
144.Bl -tag -width FTS_DEFAULT
145.It Dv FTS_D
146A directory being visited in pre-order.
147.It Dv FTS_DC
148A directory that causes a cycle in the tree.
149(The
150.Fa fts_cycle
151field of the
152.Vt FTSENT
153structure will be filled in as well.)
154.It Dv FTS_DEFAULT
155Any
156.Vt FTSENT
157structure that represents a file type not explicitly described
158by one of the other
159.Fa fts_info
160values.
161.It Dv FTS_DNR
162A directory which cannot be read.
163This is an error return, and the
164.Fa fts_errno
165field will be set to indicate what caused the error.
166.It Dv FTS_DOT
167A file named
168.Ql .\&
169or
170.Ql ..\&
171which was not specified as a file name to
172.Fn fts_open
173(see
174.Dv FTS_SEEDOT ) .
175.It Dv FTS_DP
176A directory being visited in post-order.
177The contents of the
178.Vt FTSENT
179structure will be unchanged from when
180it was returned in pre-order, i.e. with the
181.Fa fts_info
182field set to
183.Dv FTS_D .
184.It Dv FTS_ERR
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_F
189A regular file.
190.It Dv FTS_NS
191A file for which no
192.Xr stat 2
193information was available.
194The contents of the
195.Fa fts_statp
196field are undefined.
197This is an error return, and the
198.Fa fts_errno
199field will be set to indicate what caused the error.
200.It Dv FTS_NSOK
201A file for which no
202.Xr stat 2
203information was requested.
204The contents of the
205.Fa fts_statp
206field are undefined.
207.It Dv FTS_SL
208A symbolic link.
209.It Dv FTS_SLNONE
210A symbolic link with a non-existent target.
211The contents of the
212.Fa fts_statp
213field reference the file characteristic information for the symbolic link
214itself.
215.El
216.It Fa fts_accpath
217A path for accessing the file from the current directory.
218.It Fa fts_path
219The path for the file relative to the root of the traversal.
220This path contains the path specified to
221.Fn fts_open
222as a prefix.
223.It Fa fts_pathlen
224The length of the string referenced by
225.Fa fts_path .
226.It Fa fts_name
227The name of the file.
228.It Fa fts_namelen
229The length of the string referenced by
230.Fa fts_name .
231.It Fa fts_level
232The depth of the traversal, numbered from \-1 to N, where this file
233was found.
234The
235.Vt FTSENT
236structure representing the parent of the starting point (or root)
237of the traversal is numbered
238.Dv FTS_ROOTPARENTLEVEL
239(\-1), and the
240.Vt FTSENT
241structure for the root
242itself is numbered
243.Dv FTS_ROOTLEVEL
244(0).
245.It Fa fts_errno
246Upon return of a
247.Vt FTSENT
248structure from the
249.Fn fts_children
250or
251.Fn fts_read
252functions, with its
253.Fa fts_info
254field set to
255.Dv FTS_DNR ,
256.Dv FTS_ERR
257or
258.Dv FTS_NS ,
259the
260.Fa fts_errno
261field contains the value of the external variable
262.Va errno
263specifying the cause of the error.
264Otherwise, the contents of the
265.Fa fts_errno
266field are undefined.
267.It Fa fts_number
268This field is provided for the use of the application program and is
269not modified by the
270.Nm
271functions.
272It is initialized to 0.
273.It Fa fts_pointer
274This field is provided for the use of the application program and is
275not modified by the
276.Nm
277functions.
278It is initialized to
279.Dv NULL .
280.It Fa fts_parent
281A pointer to the
282.Vt FTSENT
283structure referencing the file in the hierarchy
284immediately above the current file, i.e. the directory of which this
285file is a member.
286A parent structure for the initial entry point is provided as well,
287however, only the
288.Fa fts_level ,
289.Fa fts_number
290and
291.Fa fts_pointer
292fields are guaranteed to be initialized.
293.It Fa fts_link
294Upon return from the
295.Fn fts_children
296function, the
297.Fa fts_link
298field points to the next structure in the NULL-terminated linked list of
299directory members.
300Otherwise, the contents of the
301.Fa fts_link
302field are undefined.
303.It Fa fts_cycle
304If a directory causes a cycle in the hierarchy (see
305.Dv FTS_DC ) ,
306either because
307of a hard link between two directories, or a symbolic link pointing to a
308directory, the
309.Fa fts_cycle
310field of the structure will point to the
311.Vt FTSENT
312structure in the hierarchy that references the same file as the current
313.Vt FTSENT
314structure.
315Otherwise, the contents of the
316.Fa fts_cycle
317field are undefined.
318.It Fa fts_statp
319A pointer to
320.Xr stat 2
321information for the file.
322.El
323.Pp
324A single buffer is used for all of the paths of all of the files in the
325file hierarchy.
326Therefore, the
327.Fa fts_path
328and
329.Fa fts_accpath
330fields are guaranteed to be
331.Dv NUL Ns -terminated
332.Em only
333for the file most recently returned by
334.Fn fts_read .
335To use these fields to reference any files represented by other
336.Vt FTSENT
337structures will require that the path buffer be modified using the
338information contained in that
339.Vt FTSENT
340structure's
341.Fa fts_pathlen
342field.
343Any such modifications should be undone before further calls to
344.Fn fts_read
345are attempted.
346The
347.Fa fts_name
348field is always
349.Dv NUL Ns -terminated .
350.Sh FTS_OPEN
351The
352.Fn fts_open
353function takes a pointer to an array of character pointers naming one
354or more paths which make up a logical file hierarchy to be traversed.
355The array must be terminated by a
356.Dv NULL
357pointer.
358.Pp
359There are
360a number of options, at least one of which (either
361.Dv FTS_LOGICAL
362or
363.Dv FTS_PHYSICAL )
364must be specified.
365The options are selected by
366.Em or Ns 'ing
367the following values:
368.Bl -tag -width "FTS_PHYSICAL"
369.It Dv FTS_COMFOLLOW
370This option causes any symbolic link specified as a root path to be
371followed immediately whether or not
372.Dv FTS_LOGICAL
373is also specified.
374.It Dv FTS_LOGICAL
375This option causes the
376.Nm
377routines to return
378.Vt FTSENT
379structures for the targets of symbolic links
380instead of the symbolic links themselves.
381If this option is set, the only symbolic links for which
382.Vt FTSENT
383structures
384are returned to the application are those referencing non-existent files.
385Either
386.Dv FTS_LOGICAL
387or
388.Dv FTS_PHYSICAL
389.Em must
390be provided to the
391.Fn fts_open
392function.
393.It Dv FTS_NOCHDIR
394As a performance optimization, the
395.Nm
396functions change directories as they walk the file hierarchy.
397This has the side-effect that an application cannot rely on being
398in any particular directory during the traversal.
399The
400.Dv FTS_NOCHDIR
401option turns off this optimization, and the
402.Nm
403functions will not change the current directory.
404Note that applications should not themselves change their current directory
405and try to access files unless
406.Dv FTS_NOCHDIR
407is specified and absolute
408pathnames were provided as arguments to
409.Fn fts_open .
410.It Dv FTS_NOSTAT
411By default, returned
412.Vt FTSENT
413structures reference file characteristic information (the
414.Fa statp
415field) for each file visited.
416This option relaxes that requirement as a performance optimization,
417allowing the
418.Nm
419functions to set the
420.Fa fts_info
421field to
422.Dv FTS_NSOK
423and leave the contents of the
424.Fa statp
425field undefined.
426.It Dv FTS_PHYSICAL
427This option causes the
428.Nm
429routines to return
430.Vt FTSENT
431structures for symbolic links themselves instead
432of the target files they point to.
433If this option is set,
434.Vt FTSENT
435structures for all symbolic links in the
436hierarchy are returned to the application.
437Either
438.Dv FTS_LOGICAL
439or
440.Dv FTS_PHYSICAL
441.Em must
442be provided to the
443.Fn fts_open
444function.
445.It Dv FTS_SEEDOT
446By default, unless they are specified as path arguments to
447.Fn fts_open ,
448any files named
449.Ql .\&
450or
451.Ql ..\&
452encountered in the file hierarchy are ignored.
453This option causes the
454.Nm
455routines to return
456.Vt FTSENT
457structures for them.
458.It Dv FTS_XDEV
459This option prevents
460.Nm
461from descending into directories that have a different device number
462than the file from which the descent began.
463.El
464.Pp
465The argument
466.Fn compar
467specifies a user-defined function which may be used to order the traversal
468of the hierarchy.
469It
470takes two pointers to pointers to
471.Vt FTSENT
472structures as arguments and
473should return a negative value, zero, or a positive value to indicate
474if the file referenced by its first argument comes before, in any order
475with respect to, or after, the file referenced by its second argument.
476The
477.Fa fts_accpath ,
478.Fa fts_path
479and
480.Fa fts_pathlen
481fields of the
482.Vt FTSENT
483structures may
484.Em never
485be used in this comparison.
486If the
487.Fa fts_info
488field is set to
489.Dv FTS_NS
490or
491.Dv FTS_NSOK ,
492the
493.Fa fts_statp
494field may not either.
495If the
496.Fn compar
497argument is
498.Dv NULL ,
499the directory traversal order is in the order listed in
500.Fa path_argv
501for the root paths, and in the order listed in the directory for
502everything else.
503.Sh FTS_READ
504The
505.Fn fts_read
506function returns a pointer to an
507.Vt FTSENT
508structure describing a file in
509the hierarchy.
510Directories (that are readable and do not cause cycles) are visited at
511least twice, once in pre-order and once in post-order.
512All other files are visited at least once.
513(Hard links between directories that do not cause cycles or symbolic
514links to symbolic links may cause files to be visited more than once,
515or directories more than twice.)
516.Pp
517If all the members of the hierarchy have been returned,
518.Fn fts_read
519returns
520.Dv NULL
521and sets the external variable
522.Va errno
523to 0.
524If an error unrelated to a file in the hierarchy occurs,
525.Fn fts_read
526returns
527.Dv NULL
528and sets
529.Va errno
530appropriately.
531If an error related to a returned file occurs, a pointer to an
532.Vt FTSENT
533structure is returned, and
534.Va errno
535may or may not have been set (see
536.Fa fts_info ) .
537.Pp
538The
539.Vt FTSENT
540structures returned by
541.Fn fts_read
542may be overwritten after a call to
543.Fn fts_close
544on the same file hierarchy stream, or, after a call to
545.Fn fts_read
546on the same file hierarchy stream unless they represent a file of type
547directory, in which case they will not be overwritten until after a call to
548.Fn fts_read
549after the
550.Vt FTSENT
551structure has been returned by the function
552.Fn fts_read
553in post-order.
554.Sh FTS_CHILDREN
555The
556.Fn fts_children
557function returns a pointer to an
558.Vt FTSENT
559structure describing the first entry in a NULL-terminated linked list of
560the files in the directory represented by the
561.Vt FTSENT
562structure most recently returned by
563.Fn fts_read .
564The list is linked through the
565.Fa fts_link
566field of the
567.Vt FTSENT
568structure, and is ordered by the user-specified comparison function, if any.
569Repeated calls to
570.Fn fts_children
571will recreate this linked list.
572.Pp
573As a special case, if
574.Fn fts_read
575has not yet been called for a hierarchy,
576.Fn fts_children
577will return a pointer to the files in the logical directory specified to
578.Fn fts_open ,
579i.e. the arguments specified to
580.Fn fts_open .
581Otherwise, if the
582.Vt FTSENT
583structure most recently returned by
584.Fn fts_read
585is not a directory being visited in pre-order,
586or the directory does not contain any files,
587.Fn fts_children
588returns
589.Dv NULL
590and sets
591.Va errno
592to zero.
593If an error occurs,
594.Fn fts_children
595returns
596.Dv NULL
597and sets
598.Va errno
599appropriately.
600.Pp
601The
602.Vt FTSENT
603structures returned by
604.Fn fts_children
605may be overwritten after a call to
606.Fn fts_children ,
607.Fn fts_close
608or
609.Fn fts_read
610on the same file hierarchy stream.
611.Pp
612.Em Option
613may be set to the following value:
614.Bl -tag -width FTS_NAMEONLY
615.It Dv FTS_NAMEONLY
616Only the names of the files are needed.
617The contents of all the fields in the returned linked list of structures
618are undefined with the exception of the
619.Fa fts_name
620and
621.Fa fts_namelen
622fields.
623.El
624.Sh FTS_SET
625The function
626.Fn fts_set
627allows the user application to determine further processing for the
628file
629.Fa f
630of the stream
631.Fa ftsp .
632The
633.Fn fts_set
634function
635returns 0 on success, and \-1 if an error occurs.
636.Em Option
637must be set to one of the following values:
638.Bl -tag -width FTS_PHYSICAL
639.It Dv FTS_AGAIN
640Re-visit the file; any file type may be re-visited.
641The next call to
642.Fn fts_read
643will return the referenced file.
644The
645.Fa fts_stat
646and
647.Fa fts_info
648fields of the structure will be reinitialized at that time,
649but no other fields will have been changed.
650This option is meaningful only for the most recently returned
651file from
652.Fn fts_read .
653Normal use is for post-order directory visits, where it causes the
654directory to be re-visited (in both pre and post-order) as well as all
655of its descendants.
656.It Dv FTS_FOLLOW
657The referenced file must be a symbolic link.
658If the referenced file is the one most recently returned by
659.Fn fts_read ,
660the next call to
661.Fn fts_read
662returns the file with the
663.Fa fts_info
664and
665.Fa fts_statp
666fields reinitialized to reflect the target of the symbolic link instead
667of the symbolic link itself.
668If the file is one of those most recently returned by
669.Fn fts_children ,
670the
671.Fa fts_info
672and
673.Fa fts_statp
674fields of the structure, when returned by
675.Fn fts_read ,
676will reflect the target of the symbolic link instead of the symbolic link
677itself.
678In either case, if the target of the symbolic link does not exist the
679fields of the returned structure will be unchanged and the
680.Fa fts_info
681field will be set to
682.Dv FTS_SLNONE .
683.Pp
684If the target of the link is a directory, the pre-order return, followed
685by the return of all of its descendants, followed by a post-order return,
686is done.
687.It Dv FTS_SKIP
688No descendants of this file are visited.
689The file may be one of those most recently returned by either
690.Fn fts_children
691or
692.Fn fts_read .
693.El
694.Sh FTS_CLOSE
695The
696.Fn fts_close
697function closes a file hierarchy stream
698.Fa ftsp
699and restores the current directory to the directory from which
700.Fn fts_open
701was called to open
702.Fa ftsp .
703The
704.Fn fts_close
705function
706returns 0 on success, and \-1 if an error occurs.
707.Sh ERRORS
708The function
709.Fn fts_open
710may fail and set
711.Va errno
712for any of the errors specified for the library functions
713.Xr open 2
714and
715.Xr malloc 3 .
716.Pp
717The function
718.Fn fts_close
719may fail and set
720.Va errno
721for any of the errors specified for the library functions
722.Xr chdir 2
723and
724.Xr close 2 .
725.Pp
726The functions
727.Fn fts_read
728and
729.Fn fts_children
730may fail and set
731.Va errno
732for any of the errors specified for the library functions
733.Xr chdir 2 ,
734.Xr malloc 3 ,
735.Xr opendir 3 ,
736.Xr readdir 3
737and
738.Xr stat 2 .
739.Pp
740In addition,
741.Fn fts_children ,
742.Fn fts_open
743and
744.Fn fts_set
745may fail and set
746.Va errno
747as follows:
748.Bl -tag -width Er
749.It Bq Er EINVAL
750The options were invalid.
751.El
752.Sh SEE ALSO
753.Xr find 1 ,
754.Xr chdir 2 ,
755.Xr stat 2 ,
756.Xr qsort 3
757.Sh STANDARDS
758The
759.Nm
760utility is expected to be included in a future
761.St -p1003.1-88
762revision.