1NFTW(3P) POSIX Programmer's Manual NFTW(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 nftw — walk a file tree
14
16 #include <ftw.h>
17 int nftw(const char *path, int (*fn)(const char *,
19 const struct stat *, int, struct FTW *), int fd_limit, int flags);
20
22 The nftw() function shall recursively descend the directory hierarchy
23 rooted in path. The nftw() function has a similar effect to ftw()
24 except that it takes an additional argument flags, which is a bitwise-
25 inclusive OR of zero or more of the following flags:
26 FTW_CHDIR If set, nftw() shall change the current working directory
28 to each directory as it reports files in that directory. If
29 clear, nftw() shall not change the current working direc‐
30 tory.
31 FTW_DEPTH If set, nftw() shall report all files in a directory before
33 reporting the directory itself. If clear, nftw() shall
34 report any directory before reporting the files in that
35 directory.
36 FTW_MOUNT If set, nftw() shall only report files in the same file
38 system as path. If clear, nftw() shall report all files
39 encountered during the walk.
40 FTW_PHYS If set, nftw() shall perform a physical walk and shall not
42 follow symbolic links.
43 If FTW_PHYS is clear and FTW_DEPTH is set, nftw() shall follow links
45 instead of reporting them, but shall not report any directory that
46 would be a descendant of itself. If FTW_PHYS is clear and FTW_DEPTH is
47 clear, nftw() shall follow links instead of reporting them, but shall
48 not report the contents of any directory that would be a descendant of
49 itself.
50 At each file it encounters, nftw() shall call the user-supplied func‐
52 tion fn with four arguments:
53 * The first argument is the pathname of the object.
55 * The second argument is a pointer to the stat buffer containing
57 information on the object, filled in as if fstatat(), stat(), or
58 lstat() had been called to retrieve the information.
59 * The third argument is an integer giving additional information. Its
61 value is one of the following:
62 FTW_D The object is a directory.
64 FTW_DNR The object is a directory that cannot be read. The fn
66 function shall not be called for any of its descendants.
67 FTW_DP The object is a directory and subdirectories have been
69 visited. (This condition shall only occur if the
70 FTW_DEPTH flag is included in flags.)
71 FTW_F The object is a non-directory file.
73 FTW_NS The stat() function failed on the object because of lack
75 of appropriate permission. The stat buffer passed to fn
76 is undefined. Failure of stat() for any other reason is
77 considered an error and nftw() shall return −1.
78 FTW_SL The object is a symbolic link. (This condition shall only
80 occur if the FTW_PHYS flag is included in flags.)
81 FTW_SLN The object is a symbolic link that does not name an
83 existing file. (This condition shall only occur if the
84 FTW_PHYS flag is not included in flags.)
85 * The fourth argument is a pointer to an FTW structure. The value of
87 base is the offset of the object's filename in the pathname passed
88 as the first argument to fn. The value of level indicates depth
89 relative to the root of the walk, where the root level is 0.
90 The results are unspecified if the application-supplied fn function
92 does not preserve the current working directory.
93 The argument fd_limit sets the maximum number of file descriptors that
95 shall be used by nftw() while traversing the file tree. At most one
96 file descriptor shall be used for each directory level.
97 The nftw() function need not be thread-safe.
99
101 The nftw() function shall continue until the first of the following
102 conditions occurs:
103 * An invocation of fn shall return a non-zero value, in which case
105 nftw() shall return that value.
106 * The nftw() function detects an error other than [EACCES] (see
108 FTW_DNR and FTW_NS above), in which case nftw() shall return −1 and
109 set errno to indicate the error.
110 * The tree is exhausted, in which case nftw() shall return 0.
112
114 The nftw() function shall fail if:
115 EACCES Search permission is denied for any component of path or read
117 permission is denied for path, or fn returns −1 and does not
118 reset errno.
119 ELOOP A loop exists in symbolic links encountered during resolution of
121 the path argument.
122 ENAMETOOLONG
124 The length of a component of a pathname is longer than
125 {NAME_MAX}.
126 ENOENT A component of path does not name an existing file or path is an
128 empty string.
129 ENOTDIR
131 A component of path names an existing file that is neither a
132 directory nor a symbolic link to a directory.
133 EOVERFLOW
135 A field in the stat structure cannot be represented correctly in
136 the current programming environment for one or more files found
137 in the file hierarchy.
138 The nftw() function may fail if:
140 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
142 resolution of the path argument.
143 EMFILE All file descriptors available to the process are currently
145 open.
146 ENAMETOOLONG
148 The length of a pathname exceeds {PATH_MAX}, or pathname resolu‐
149 tion of a symbolic link produced an intermediate result with a
150 length that exceeds {PATH_MAX}.
151 ENFILE Too many files are currently open in the system.
153 In addition, errno may be set if the function pointed to by fn causes
155 errno to be set.
156 The following sections are informative.
158
160 The following program traverses the directory tree under the path named
161 in its first command-line argument, or under the current directory if
162 no argument is supplied. It displays various information about each
163 file. The second command-line argument can be used to specify charac‐
164 ters that control the value assigned to the flags argument when calling
165 nftw().
166 #include <ftw.h>
168 #include <stdio.h>
169 #include <stdlib.h>
170 #include <string.h>
171 #include <stdint.h>
172 static int
174 display_info(const char *fpath, const struct stat *sb,
175 int tflag, struct FTW *ftwbuf)
176 {
177 printf("%-3s %2d %7jd %-40s %d %s\n",
178 (tflag == FTW_D) ? "d" : (tflag == FTW_DNR) ? "dnr" :
179 (tflag == FTW_DP) ? "dp" : (tflag == FTW_F) ?
180 (S_ISBLK(sb->st_mode) ? "f b" :
181 S_ISCHR(sb->st_mode) ? "f c" :
182 S_ISFIFO(sb->st_mode) ? "f p" :
183 S_ISREG(sb->st_mode) ? "f r" :
184 S_ISSOCK(sb->st_mode) ? "f s" : "f ?") :
185 (tflag == FTW_NS) ? "ns" : (tflag == FTW_SL) ? "sl" :
186 (tflag == FTW_SLN) ? "sln" : "?",
187 ftwbuf->level, (intmax_t) sb->st_size,
188 fpath, ftwbuf->base, fpath + ftwbuf->base);
189 return 0; /* To tell nftw() to continue */
190 }
191 int
193 main(int argc, char *argv[])
194 {
195 int flags = 0;
196 if (argc > 2 && strchr(argv[2], 'd') != NULL)
198 flags |= FTW_DEPTH;
199 if (argc > 2 && strchr(argv[2], 'p') != NULL)
200 flags |= FTW_PHYS;
201 if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags) == -1)
203 {
204 perror("nftw");
205 exit(EXIT_FAILURE);
206 }
207 exit(EXIT_SUCCESS);
209 }
210
212 The nftw() function may allocate dynamic storage during its operation.
213 If nftw() is forcibly terminated, such as by longjmp() or siglongjmp()
214 being executed by the function pointed to by fn or an interrupt rou‐
215 tine, nftw() does not have a chance to free that storage, so it remains
216 permanently allocated. A safe way to handle interrupts is to store the
217 fact that an interrupt has occurred, and arrange to have the function
218 pointed to by fn return a non-zero value at its next invocation.
219
221 None.
222
224 None.
225
227 fdopendir(), fstatat(), readdir()
228 The Base Definitions volume of POSIX.1‐2008, <ftw.h>
230
232 Portions of this text are reprinted and reproduced in electronic form
233 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
234 -- Portable Operating System Interface (POSIX), The Open Group Base
235 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
236 cal and Electronics Engineers, Inc and The Open Group. (This is
237 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
238 event of any discrepancy between this version and the original IEEE and
239 The Open Group Standard, the original IEEE and The Open Group Standard
240 is the referee document. The original Standard can be obtained online
241 at http://www.unix.org/online.html .
242 Any typographical or formatting errors that appear in this page are
244 most likely to have been introduced during the conversion of the source
245 files to man page format. To report such errors, see https://www.ker‐
246 nel.org/doc/man-pages/reporting_bugs.html .
247IEEE/The Open Group 2013 NFTW(3P)