1FTW(3) Linux Programmer's Manual FTW(3)
2
6 ftw, nftw - file tree walk
7
9 #include <ftw.h>
10 int ftw(const char *dirpath,
12 int (*fn) (const char *fpath, const struct stat *sb,
13 int typeflag),
14 int nopenfd);
15 #define _XOPEN_SOURCE 500 /* See feature_test_macros(7) */
17 #include <ftw.h>
18 int nftw(const char *dirpath,
20 int (*fn) (const char *fpath, const struct stat *sb,
21 int typeflag, struct FTW *ftwbuf),
22 int nopenfd, int flags);
23
25 ftw() walks through the directory tree that is located under the direc‐
26 tory dirpath, and calls fn() once for each entry in the tree. By
27 default, directories are handled before the files and subdirectories
28 they contain (preorder traversal).
29 To avoid using up all of the calling process's file descriptors,
31 nopenfd specifies the maximum number of directories that ftw() will
32 hold open simultaneously. When the search depth exceeds this, ftw()
33 will become slower because directories have to be closed and reopened.
34 ftw() uses at most one file descriptor for each level in the directory
35 tree.
36 For each entry found in the tree, ftw() calls fn() with three argu‐
38 ments: fpath, sb, and typeflag. fpath is the pathname of the entry,
39 and is expressed either as a pathname relative to the calling process's
40 current working directory at the time of the call to ftw(), if dirpath
41 was expressed as a relative pathname, or as an absolute pathname, if
42 dirpath was expressed as an absolute pathname. sb is a pointer to the
43 stat structure returned by a call to stat(2) for fpath. typeflag is an
44 integer that has one of the following values:
45 FTW_F fpath is a regular file.
47 FTW_D fpath is a directory.
49 FTW_DNR
51 fpath is a directory which can't be read.
52 FTW_NS The stat(2) call failed on fpath, which is not a symbolic link.
54 If fpath is a symbolic link and stat(2) failed, POSIX.1-2001
56 states that it is undefined whether FTW_NS or FTW_SL (see below)
57 is passed in typeflag.
58 To stop the tree walk, fn() returns a nonzero value; this value will
60 become the return value of ftw(). As long as fn() returns 0, ftw()
61 will continue either until it has traversed the entire tree, in which
62 case it will return zero, or until it encounters an error (such as a
63 malloc(3) failure), in which case it will return -1.
64 Because ftw() uses dynamic data structures, the only safe way to exit
66 out of a tree walk is to return a nonzero value from fn(). To allow a
67 signal to terminate the walk without causing a memory leak, have the
68 handler set a global flag that is checked by fn(). Don't use
69 longjmp(3) unless the program is going to terminate.
70 nftw()
72 The function nftw() is the same as ftw(), except that it has one addi‐
73 tional argument, flags, and calls fn() with one more argument, ftwbuf.
74 This flags argument is formed by ORing zero or more of the following
76 flags:
77 FTW_ACTIONRETVAL (since glibc 2.3.3)
79 If this glibc-specific flag is set, then nftw() handles the
80 return value from fn() differently. fn() should return one of
81 the following values:
82 FTW_CONTINUE
84 Instructs nftw() to continue normally.
85 FTW_SKIP_SIBLINGS
87 If fn() returns this value, then siblings of the current
88 entry will be skipped, and processing continues in the
89 parent.
90 FTW_SKIP_SUBTREE
92 If fn() is called with an entry that is a directory
93 (typeflag is FTW_D), this return value will prevent
94 objects within that directory from being passed as argu‐
95 ments to fn(). nftw() continues processing with the next
96 sibling of the directory.
97 FTW_STOP
99 Causes nftw() to return immediately with the return value
100 FTW_STOP.
101 Other return values could be associated with new actions in the
103 future; fn() should not return values other than those listed
104 above.
105 The feature test macro _GNU_SOURCE must be defined (before
107 including any header files) in order to obtain the definition of
108 FTW_ACTIONRETVAL from <ftw.h>.
109 FTW_CHDIR
111 If set, do a chdir(2) to each directory before handling its con‐
112 tents. This is useful if the program needs to perform some
113 action in the directory in which fpath resides.
114 FTW_DEPTH
116 If set, do a post-order traversal, that is, call fn() for the
117 directory itself after handling the contents of the directory
118 and its subdirectories. (By default, each directory is handled
119 before its contents.)
120 FTW_MOUNT
122 If set, stay within the same file system (i.e., do not cross
123 mount points).
124 FTW_PHYS
126 If set, do not follow symbolic links. (This is what you want.)
127 If not set, symbolic links are followed, but no file is reported
128 twice.
129 If FTW_PHYS is not set, but FTW_DEPTH is set, then the function
131 fn() is never called for a directory that would be a descendant
132 of itself.
133 For each entry in the directory tree, nftw() calls fn() with four argu‐
135 ments. fpath and sb are as for ftw(). typeflag may receive any of the
136 same values as with ftw(), or any of the following values:
137 FTW_DP fpath is a directory, and FTW_DEPTH was specified in flags. All
139 of the files and subdirectories within fpath have been pro‐
140 cessed.
141 FTW_SL fpath is a symbolic link, and FTW_PHYS was set in flags.
143 FTW_SLN
145 fpath is a symbolic link pointing to a nonexistent file. (This
146 occurs only if FTW_PHYS is not set.)
147 The fourth argument that nftw() supplies when calling fn() is a struc‐
149 ture of type FTW:
150 struct FTW {
152 int base;
153 int level;
154 };
155 base is the offset of the filename (i.e., basename component) in the
157 pathname given in fpath. level is the depth of fpath in the directory
158 tree, relative to the root of the tree (dirpath, which has depth 0).
159
161 These functions return 0 on success, and -1 if an error occurs.
162 If fn() returns nonzero, then the tree walk is terminated and the value
164 returned by fn() is returned as the result of ftw() or nftw().
165 If nftw() is called with the FTW_ACTIONRETVAL flag, then the only
167 nonzero value that should be used by fn() to terminate the tree walk is
168 FTW_STOP, and that value is returned as the result of nftw().
169
171 POSIX.1-2001, SVr4, SUSv1. POSIX.1-2008 marks ftw() as obsolete.
172
174 POSIX.1-2001 note that the results are unspecified if fn does not pre‐
175 serve the current working directory.
176 The function nftw() and the use of FTW_SL with ftw() were introduced in
178 SUSv1.
179 On some systems ftw() will never use FTW_SL, on other systems FTW_SL
181 occurs only for symbolic links that do not point to an existing file,
182 and again on other systems ftw() will use FTW_SL for each symbolic
183 link. For predictable control, use nftw().
184 Under Linux, libc4 and libc5 and glibc 2.0.6 will use FTW_F for all
186 objects (files, symbolic links, FIFOs, etc.) that can be stat'ed but
187 are not a directory.
188 The function nftw() is available since glibc 2.1.
190 FTW_ACTIONRETVAL is glibc-specific.
192
194 The following program traverses the directory tree under the path named
195 in its first command-line argument, or under the current directory if
196 no argument is supplied. It displays various information about each
197 file. The second command-line argument can be used to specify charac‐
198 ters that control the value assigned to the flags argument when calling
199 nftw().
200 #define _XOPEN_SOURCE 500
202 #include <ftw.h>
203 #include <stdio.h>
204 #include <stdlib.h>
205 #include <string.h>
206 #include <stdint.h>
207 static int
209 display_info(const char *fpath, const struct stat *sb,
210 int tflag, struct FTW *ftwbuf)
211 {
212 printf("%-3s %2d %7jd %-40s %d %s\n",
213 (tflag == FTW_D) ? "d" : (tflag == FTW_DNR) ? "dnr" :
214 (tflag == FTW_DP) ? "dp" : (tflag == FTW_F) ? "f" :
215 (tflag == FTW_NS) ? "ns" : (tflag == FTW_SL) ? "sl" :
216 (tflag == FTW_SLN) ? "sln" : "???",
217 ftwbuf->level, (intmax_t) sb->st_size,
218 fpath, ftwbuf->base, fpath + ftwbuf->base);
219 return 0; /* To tell nftw() to continue */
220 }
221 int
223 main(int argc, char *argv[])
224 {
225 int flags = 0;
226 if (argc > 2 && strchr(argv[2], 'd') != NULL)
228 flags |= FTW_DEPTH;
229 if (argc > 2 && strchr(argv[2], 'p') != NULL)
230 flags |= FTW_PHYS;
231 if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags)
233 == -1) {
234 perror("nftw");
235 exit(EXIT_FAILURE);
236 }
237 exit(EXIT_SUCCESS);
238 }
239
241 stat(2), fts(3), readdir(3)
242
244 This page is part of release 3.53 of the Linux man-pages project. A
245 description of the project, and information about reporting bugs, can
246 be found at http://www.kernel.org/doc/man-pages/.
247Linux 2010-09-20 FTW(3)