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
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 in order to
107 obtain the definition of FTW_ACTIONRETVAL from <ftw.h>.
108 FTW_CHDIR
110 If set, do a chdir(2) to each directory before handling its con‐
111 tents. This is useful if the program needs to perform some
112 action in the directory in which fpath resides.
113 FTW_DEPTH
115 If set, do a post-order traversal, that is, call fn() for the
116 directory itself after handling the contents of the directory
117 and its subdirectories. (By default, each directory is handled
118 before its contents.)
119 FTW_MOUNT
121 If set, stay within the same file system (i.e., do not cross
122 mount points).
123 FTW_PHYS
125 If set, do not follow symbolic links. (This is what you want.)
126 If not set, symbolic links are followed, but no file is reported
127 twice.
128 If FTW_PHYS is not set, but FTW_DEPTH is set, then the function
130 fn() is never called for a directory that would be a descendant
131 of itself.
132 For each entry in the directory tree, nftw() calls fn() with four argu‐
134 ments. fpath and sb are as for ftw(). typeflag may receive any of the
135 same values as with ftw(), or any of the following values:
136 FTW_DP fpath is a directory, and FTW_DEPTH was specified in flags. All
138 of the files and subdirectories within fpath have been pro‐
139 cessed.
140 FTW_SL fpath is a symbolic link, and FTW_PHYS was set in flags.
142 FTW_SLN
144 fpath is a symbolic link pointing to a nonexistent file. (This
145 occurs only if FTW_PHYS is not set.)
146 The fourth argument that nftw() supplies when calling fn() is a struc‐
148 ture of type FTW:
149 struct FTW {
151 int base;
152 int level;
153 };
154 base is the offset of the filename (i.e., basename component) in the
156 pathname given in fpath. level is the depth of fpath in the directory
157 tree, relative to the root of the tree (dirpath, which has depth 0).
158
160 These functions return 0 on success, and -1 if an error occurs.
161 If fn() returns nonzero, then the tree walk is terminated and the value
163 returned by fn() is returned as the result of ftw() or nftw().
164 If nftw() is called with the FTW_ACTIONRETVAL flag, then the only
166 nonzero value that should be used by fn() to terminate the tree walk is
167 FTW_STOP, and that value is returned as the result of nftw().
168
170 POSIX.1-2001, SVr4, SUSv1. POSIX.1-2008 marks ftw() as obsolete.
171
173 POSIX.1-2001 note that the results are unspecified if fn does not pre‐
174 serve the current working directory.
175 The function nftw() and the use of FTW_SL with ftw() were introduced in
177 SUSv1.
178 On some systems ftw() will never use FTW_SL, on other systems FTW_SL
180 occurs only for symbolic links that do not point to an existing file,
181 and again on other systems ftw() will use FTW_SL for each symbolic
182 link. For predictable control, use nftw().
183 Under Linux, libc4 and libc5 and glibc 2.0.6 will use FTW_F for all
185 objects (files, symbolic links, FIFOs, etc.) that can be stat'ed but
186 are not a directory.
187 The function nftw() is available since glibc 2.1.
189 FTW_ACTIONRETVAL is glibc-specific.
191
193 The following program traverses the directory tree under the path named
194 in its first command-line argument, or under the current directory if
195 no argument is supplied. It displays various information about each
196 file. The second command-line argument can be used to specify charac‐
197 ters that control the value assigned to the flags argument when calling
198 nftw().
199 #define _XOPEN_SOURCE 500
201 #include <ftw.h>
202 #include <stdio.h>
203 #include <stdlib.h>
204 #include <string.h>
205 #include <stdint.h>
206 static int
208 display_info(const char *fpath, const struct stat *sb,
209 int tflag, struct FTW *ftwbuf)
210 {
211 printf("%-3s %2d %7jd %-40s %d %s\n",
212 (tflag == FTW_D) ? "d" : (tflag == FTW_DNR) ? "dnr" :
213 (tflag == FTW_DP) ? "dp" : (tflag == FTW_F) ? "f" :
214 (tflag == FTW_NS) ? "ns" : (tflag == FTW_SL) ? "sl" :
215 (tflag == FTW_SLN) ? "sln" : "???",
216 ftwbuf->level, (intmax_t) sb->st_size,
217 fpath, ftwbuf->base, fpath + ftwbuf->base);
218 return 0; /* To tell nftw() to continue */
219 }
220 int
222 main(int argc, char *argv[])
223 {
224 int flags = 0;
225 if (argc > 2 && strchr(argv[2], 'd') != NULL)
227 flags |= FTW_DEPTH;
228 if (argc > 2 && strchr(argv[2], 'p') != NULL)
229 flags |= FTW_PHYS;
230 if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags)
232 == -1) {
233 perror("nftw");
234 exit(EXIT_FAILURE);
235 }
236 exit(EXIT_SUCCESS);
237 }
238
240 stat(2), fts(3), readdir(3), feature_test_macros(7)
241
243 This page is part of release 3.25 of the Linux man-pages project. A
244 description of the project, and information about reporting bugs, can
245 be found at http://www.kernel.org/doc/man-pages/.
246Linux 2010-06-10 FTW(3)