1fts(3) Library Functions Manual fts(3)
2
6 fts, fts_open, fts_read, fts_children, fts_set, fts_close - traverse a
7 file hierarchy
8
10 Standard C library (libc, -lc)
11
13 #include <sys/types.h>
14 #include <sys/stat.h>
15 #include <fts.h>
16 FTS *fts_open(char * const *path_argv, int options,
18 int (*compar)(const FTSENT **, const FTSENT **));
19 FTSENT *fts_read(FTS *ftsp);
21 FTSENT *fts_children(FTS *ftsp, int instr);
23 int fts_set(FTS *ftsp, FTSENT *f, int instr);
25 int fts_close(FTS *ftsp);
27
29 The fts functions are provided for traversing file hierarchies. A sim‐
30 ple overview is that the fts_open() function returns a "handle" (of
31 type FTS *) that refers to a file hierarchy "stream". This handle is
32 then supplied to the other fts functions. The function fts_read() re‐
33 turns a pointer to a structure describing one of the files in the file
34 hierarchy. The function fts_children() returns a pointer to a linked
35 list of structures, each of which describes one of the files contained
36 in a directory in the hierarchy.
37 In general, directories are visited two distinguishable times; in pre‐
39 order (before any of their descendants are visited) and in postorder
40 (after all of their descendants have been visited). Files are visited
41 once. It is possible to walk the hierarchy "logically" (visiting the
42 files that symbolic links point to) or physically (visiting the sym‐
43 bolic links themselves), order the walk of the hierarchy or prune
44 and/or revisit portions of the hierarchy.
45 Two structures (and associated types) are defined in the include file
47 <fts.h>. The first type is FTS, the structure that represents the file
48 hierarchy itself. The second type is FTSENT, the structure that repre‐
49 sents a file in the file hierarchy. Normally, an FTSENT structure is
50 returned for every file in the file hierarchy. In this manual page,
51 "file" and "FTSENT structure" are generally interchangeable.
52 The FTSENT structure contains fields describing a file. The structure
54 contains at least the following fields (there are additional fields
55 that should be considered private to the implementation):
56 typedef struct _ftsent {
58 unsigned short fts_info; /* flags for FTSENT structure */
59 char *fts_accpath; /* access path */
60 char *fts_path; /* root path */
61 short fts_pathlen; /* strlen(fts_path) +
62 strlen(fts_name) */
63 char *fts_name; /* filename */
64 short fts_namelen; /* strlen(fts_name) */
65 short fts_level; /* depth (-1 to N) */
66 int fts_errno; /* file errno */
67 long fts_number; /* local numeric value */
68 void *fts_pointer; /* local address value */
69 struct _ftsent *fts_parent; /* parent directory */
70 struct _ftsent *fts_link; /* next file structure */
71 struct _ftsent *fts_cycle; /* cycle structure */
72 struct stat *fts_statp; /* [l]stat(2) information */
73 } FTSENT;
74 These fields are defined as follows:
76 fts_info
78 One of the following values describing the returned FTSENT
79 structure and the file it represents. With the exception of di‐
80 rectories without errors (FTS_D), all of these entries are ter‐
81 minal, that is, they will not be revisited, nor will any of
82 their descendants be visited.
83 FTS_D A directory being visited in preorder.
85 FTS_DC A directory that causes a cycle in the tree. (The
87 fts_cycle field of the FTSENT structure will be filled in
88 as well.)
89 FTS_DEFAULT
91 Any FTSENT structure that represents a file type not ex‐
92 plicitly described by one of the other fts_info values.
93 FTS_DNR
95 A directory which cannot be read. This is an error re‐
96 turn, and the fts_errno field will be set to indicate
97 what caused the error.
98 FTS_DOT
100 A file named "." or ".." which was not specified as a
101 filename to fts_open() (see FTS_SEEDOT).
102 FTS_DP A directory being visited in postorder. The contents of
104 the FTSENT structure will be unchanged from when it was
105 returned in preorder, that is, with the fts_info field
106 set to FTS_D.
107 FTS_ERR
109 This is an error return, and the fts_errno field will be
110 set to indicate what caused the error.
111 FTS_F A regular file.
113 FTS_NS A file for which no [l]stat(2) information was available.
115 The contents of the fts_statp field are undefined. This
116 is an error return, and the fts_errno field will be set
117 to indicate what caused the error.
118 FTS_NSOK
120 A file for which no [l]stat(2) information was requested.
121 The contents of the fts_statp field are undefined.
122 FTS_SL A symbolic link.
124 FTS_SLNONE
126 A symbolic link with a nonexistent target. The contents
127 of the fts_statp field reference the file characteristic
128 information for the symbolic link itself.
129 fts_accpath
131 A path for accessing the file from the current directory.
132 fts_path
134 The path for the file relative to the root of the traversal.
135 This path contains the path specified to fts_open() as a prefix.
136 fts_pathlen
138 The sum of the lengths of the strings referenced by fts_path and
139 fts_name.
140 fts_name
142 The name of the file.
143 fts_namelen
145 The length of the string referenced by fts_name.
146 fts_level
148 The depth of the traversal, numbered from -1 to N, where this
149 file was found. The FTSENT structure representing the parent of
150 the starting point (or root) of the traversal is numbered -1,
151 and the FTSENT structure for the root itself is numbered 0.
152 fts_errno
154 If fts_children() or fts_read() returns an FTSENT structure
155 whose fts_info field is set to FTS_DNR, FTS_ERR, or FTS_NS, the
156 fts_errno field contains the error number (i.e., the errno
157 value) specifying the cause of the error. Otherwise, the con‐
158 tents of the fts_errno field are undefined.
159 fts_number
161 This field is provided for the use of the application program
162 and is not modified by the fts functions. It is initialized to
163 0.
164 fts_pointer
166 This field is provided for the use of the application program
167 and is not modified by the fts functions. It is initialized to
168 NULL.
169 fts_parent
171 A pointer to the FTSENT structure referencing the file in the
172 hierarchy immediately above the current file, that is, the di‐
173 rectory of which this file is a member. A parent structure for
174 the initial entry point is provided as well, however, only the
175 fts_level, fts_number, and fts_pointer fields are guaranteed to
176 be initialized.
177 fts_link
179 Upon return from the fts_children() function, the fts_link field
180 points to the next structure in the NULL-terminated linked list
181 of directory members. Otherwise, the contents of the fts_link
182 field are undefined.
183 fts_cycle
185 If a directory causes a cycle in the hierarchy (see FTS_DC), ei‐
186 ther because of a hard link between two directories, or a sym‐
187 bolic link pointing to a directory, the fts_cycle field of the
188 structure will point to the FTSENT structure in the hierarchy
189 that references the same file as the current FTSENT structure.
190 Otherwise, the contents of the fts_cycle field are undefined.
191 fts_statp
193 A pointer to [l]stat(2) information for the file.
194 A single buffer is used for all of the paths of all of the files in the
196 file hierarchy. Therefore, the fts_path and fts_accpath fields are
197 guaranteed to be null-terminated only for the file most recently re‐
198 turned by fts_read(). To use these fields to reference any files rep‐
199 resented by other FTSENT structures will require that the path buffer
200 be modified using the information contained in that FTSENT structure's
201 fts_pathlen field. Any such modifications should be undone before fur‐
202 ther calls to fts_read() are attempted. The fts_name field is always
203 null-terminated.
204 fts_open()
206 The fts_open() function takes a pointer to an array of character point‐
207 ers naming one or more paths which make up a logical file hierarchy to
208 be traversed. The array must be terminated by a null pointer.
209 There are a number of options, at least one of which (either FTS_LOGI‐
211 CAL or FTS_PHYSICAL) must be specified. The options are selected by
212 ORing the following values:
213 FTS_LOGICAL
215 This option causes the fts routines to return FTSENT structures
216 for the targets of symbolic links instead of the symbolic links
217 themselves. If this option is set, the only symbolic links for
218 which FTSENT structures are returned to the application are
219 those referencing nonexistent files: the fts_statp field is ob‐
220 tained via stat(2) with a fallback to lstat(2).
221 FTS_PHYSICAL
223 This option causes the fts routines to return FTSENT structures
224 for symbolic links themselves instead of the target files they
225 point to. If this option is set, FTSENT structures for all sym‐
226 bolic links in the hierarchy are returned to the application:
227 the fts_statp field is obtained via lstat(2).
228 FTS_COMFOLLOW
230 This option causes any symbolic link specified as a root path to
231 be followed immediately, as if via FTS_LOGICAL, regardless of
232 the primary mode.
233 FTS_NOCHDIR
235 As a performance optimization, the fts functions change directo‐
236 ries as they walk the file hierarchy. This has the side-effect
237 that an application cannot rely on being in any particular di‐
238 rectory during the traversal. This option turns off this opti‐
239 mization, and the fts functions will not change the current di‐
240 rectory. Note that applications should not themselves change
241 their current directory and try to access files unless
242 FTS_NOCHDIR is specified and absolute pathnames were provided as
243 arguments to fts_open().
244 FTS_NOSTAT
246 By default, returned FTSENT structures reference file character‐
247 istic information (the fts_statp field) for each file visited.
248 This option relaxes that requirement as a performance optimiza‐
249 tion, allowing the fts functions to set the fts_info field to
250 FTS_NSOK and leave the contents of the fts_statp field unde‐
251 fined.
252 FTS_SEEDOT
254 By default, unless they are specified as path arguments to
255 fts_open(), any files named "." or ".." encountered in the
256 file hierarchy are ignored. This option causes the fts routines
257 to return FTSENT structures for them.
258 FTS_XDEV
260 This option prevents fts from descending into directories that
261 have a different device number than the file from which the de‐
262 scent began.
263 The argument compar() specifies a user-defined function which may be
265 used to order the traversal of the hierarchy. It takes two pointers to
266 pointers to FTSENT structures as arguments and should return a negative
267 value, zero, or a positive value to indicate if the file referenced by
268 its first argument comes before, in any order with respect to, or af‐
269 ter, the file referenced by its second argument. The fts_accpath,
270 fts_path, and fts_pathlen fields of the FTSENT structures may never be
271 used in this comparison. If the fts_info field is set to FTS_NS or
272 FTS_NSOK, the fts_statp field may not either. If the compar() argument
273 is NULL, the directory traversal order is in the order listed in
274 path_argv for the root paths, and in the order listed in the directory
275 for everything else.
276 fts_read()
278 The fts_read() function returns a pointer to an FTSENT structure de‐
279 scribing a file in the hierarchy. Directories (that are readable and
280 do not cause cycles) are visited at least twice, once in preorder and
281 once in postorder. All other files are visited at least once. (Hard
282 links between directories that do not cause cycles or symbolic links to
283 symbolic links may cause files to be visited more than once, or direc‐
284 tories more than twice.)
285 If all the members of the hierarchy have been returned, fts_read() re‐
287 turns NULL and sets errno to 0. If an error unrelated to a file in the
288 hierarchy occurs, fts_read() returns NULL and sets errno to indicate
289 the error. If an error related to a returned file occurs, a pointer to
290 an FTSENT structure is returned, and errno may or may not have been set
291 (see fts_info).
292 The FTSENT structures returned by fts_read() may be overwritten after a
294 call to fts_close() on the same file hierarchy stream, or, after a call
295 to fts_read() on the same file hierarchy stream unless they represent a
296 file of type directory, in which case they will not be overwritten un‐
297 til after a call to fts_read() after the FTSENT structure has been re‐
298 turned by the function fts_read() in postorder.
299 fts_children()
301 The fts_children() function returns a pointer to an FTSENT structure
302 describing the first entry in a NULL-terminated linked list of the
303 files in the directory represented by the FTSENT structure most re‐
304 cently returned by fts_read(). The list is linked through the fts_link
305 field of the FTSENT structure, and is ordered by the user-specified
306 comparison function, if any. Repeated calls to fts_children() will re-
307 create this linked list.
308 As a special case, if fts_read() has not yet been called for a hierar‐
310 chy, fts_children() will return a pointer to the files in the logical
311 directory specified to fts_open(), that is, the arguments specified to
312 fts_open(). Otherwise, if the FTSENT structure most recently returned
313 by fts_read() is not a directory being visited in preorder, or the di‐
314 rectory does not contain any files, fts_children() returns NULL and
315 sets errno to zero. If an error occurs, fts_children() returns NULL
316 and sets errno to indicate the error.
317 The FTSENT structures returned by fts_children() may be overwritten af‐
319 ter a call to fts_children(), fts_close(), or fts_read() on the same
320 file hierarchy stream.
321 The instr argument is either zero or the following value:
323 FTS_NAMEONLY
325 Only the names of the files are needed. The contents of all the
326 fields in the returned linked list of structures are undefined
327 with the exception of the fts_name and fts_namelen fields.
328 fts_set()
330 The function fts_set() allows the user application to determine further
331 processing for the file f of the stream ftsp. The fts_set() function
332 returns 0 on success, and -1 if an error occurs.
333 The instr argument is either 0 (meaning "do nothing") or one of the
335 following values:
336 FTS_AGAIN
338 Revisit the file; any file type may be revisited. The next call
339 to fts_read() will return the referenced file. The fts_stat and
340 fts_info fields of the structure will be reinitialized at that
341 time, but no other fields will have been changed. This option
342 is meaningful only for the most recently returned file from
343 fts_read(). Normal use is for postorder directory visits, where
344 it causes the directory to be revisited (in both preorder and
345 postorder) as well as all of its descendants.
346 FTS_FOLLOW
348 The referenced file must be a symbolic link. If the referenced
349 file is the one most recently returned by fts_read(), the next
350 call to fts_read() returns the file with the fts_info and
351 fts_statp fields reinitialized to reflect the target of the sym‐
352 bolic link instead of the symbolic link itself. If the file is
353 one of those most recently returned by fts_children(), the
354 fts_info and fts_statp fields of the structure, when returned by
355 fts_read(), will reflect the target of the symbolic link instead
356 of the symbolic link itself. In either case, if the target of
357 the symbolic link does not exist, the fields of the returned
358 structure will be unchanged and the fts_info field will be set
359 to FTS_SLNONE.
360 If the target of the link is a directory, the preorder return,
362 followed by the return of all of its descendants, followed by a
363 postorder return, is done.
364 FTS_SKIP
366 No descendants of this file are visited. The file may be one of
367 those most recently returned by either fts_children() or
368 fts_read().
369 fts_close()
371 The fts_close() function closes the file hierarchy stream referred to
372 by ftsp and restores the current directory to the directory from which
373 fts_open() was called to open ftsp. The fts_close() function returns 0
374 on success, and -1 if an error occurs.
375
377 The function fts_open() may fail and set errno for any of the errors
378 specified for open(2) and malloc(3).
379 The function fts_close() may fail and set errno for any of the errors
381 specified for chdir(2) and close(2).
382 The functions fts_read() and fts_children() may fail and set errno for
384 any of the errors specified for chdir(2), malloc(3), opendir(3), read‐
385 dir(3), and [l]stat(2).
386 In addition, fts_children(), fts_open(), and fts_set() may fail and set
388 errno as follows:
389 EINVAL options or instr was invalid.
391
393 For an explanation of the terms used in this section, see at‐
394 tributes(7).
395 ┌──────────────────────────────────────────┬───────────────┬───────────┐
397 │Interface │ Attribute │ Value │
398 ├──────────────────────────────────────────┼───────────────┼───────────┤
399 │fts_open(), fts_set(), fts_close() │ Thread safety │ MT-Safe │
400 ├──────────────────────────────────────────┼───────────────┼───────────┤
401 │fts_read(), fts_children() │ Thread safety │ MT-Unsafe │
402 └──────────────────────────────────────────┴───────────────┴───────────┘
403
405 None.
406
408 glibc 2. 4.4BSD.
409
411 Before glibc 2.23, all of the APIs described in this man page are not
412 safe when compiling a program using the LFS APIs (e.g., when compiling
413 with -D_FILE_OFFSET_BITS=64).
414
416 find(1), chdir(2), lstat(2), stat(2), ftw(3), qsort(3)
417Linux man-pages 6.04 2023-03-30 fts(3)