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
12 nftw — walk a file tree
13
15 #include <ftw.h>
16 int nftw(const char *path, int (*fn)(const char *,
18 const struct stat *, int, struct FTW *), int fd_limit, int flags);
19
21 The nftw() function shall recursively descend the directory hierarchy
22 rooted in path. The nftw() function has a similar effect to ftw()
23 except that it takes an additional argument flags, which is a bitwise-
24 inclusive OR of zero or more of the following flags:
25 FTW_CHDIR If set, nftw() shall change the current working directory
27 to each directory as it reports files in that directory. If
28 clear, nftw() shall not change the current working direc‐
29 tory.
30 FTW_DEPTH If set, nftw() shall report all files in a directory before
32 reporting the directory itself. If clear, nftw() shall
33 report any directory before reporting the files in that
34 directory.
35 FTW_MOUNT If set, nftw() shall only report files in the same file
37 system as path. If clear, nftw() shall report all files
38 encountered during the walk.
39 FTW_PHYS If set, nftw() shall perform a physical walk and shall not
41 follow symbolic links.
42 If FTW_PHYS is clear and FTW_DEPTH is set, nftw() shall follow links
44 instead of reporting them, but shall not report any directory that
45 would be a descendant of itself. If FTW_PHYS is clear and FTW_DEPTH is
46 clear, nftw() shall follow links instead of reporting them, but shall
47 not report the contents of any directory that would be a descendant of
48 itself.
49 At each file it encounters, nftw() shall call the user-supplied func‐
51 tion fn with four arguments:
52 * The first argument is the pathname of the object.
54 * The second argument is a pointer to the stat buffer containing
56 information on the object, filled in as if fstatat(), stat(), or
57 lstat() had been called to retrieve the information.
58 * The third argument is an integer giving additional information. Its
60 value is one of the following:
61 FTW_D The object is a directory.
63 FTW_DNR The object is a directory that cannot be read. The fn
65 function shall not be called for any of its descendants.
66 FTW_DP The object is a directory and subdirectories have been
68 visited. (This condition shall only occur if the
69 FTW_DEPTH flag is included in flags.)
70 FTW_F The object is a non-directory file.
72 FTW_NS The stat() function failed on the object because of lack
74 of appropriate permission. The stat buffer passed to fn
75 is undefined. Failure of stat() for any other reason is
76 considered an error and nftw() shall return -1.
77 FTW_SL The object is a symbolic link. (This condition shall only
79 occur if the FTW_PHYS flag is included in flags.)
80 FTW_SLN The object is a symbolic link that does not name an
82 existing file. (This condition shall only occur if the
83 FTW_PHYS flag is not included in flags.)
84 * The fourth argument is a pointer to an FTW structure. The value of
86 base is the offset of the object's filename in the pathname passed
87 as the first argument to fn. The value of level indicates depth
88 relative to the root of the walk, where the root level is 0.
89 The results are unspecified if the application-supplied fn function
91 does not preserve the current working directory.
92 The argument fd_limit sets the maximum number of file descriptors that
94 shall be used by nftw() while traversing the file tree. At most one
95 file descriptor shall be used for each directory level.
96 The nftw() function need not be thread-safe.
98
100 The nftw() function shall continue until the first of the following
101 conditions occurs:
102 * An invocation of fn shall return a non-zero value, in which case
104 nftw() shall return that value.
105 * The nftw() function detects an error other than [EACCES] (see
107 FTW_DNR and FTW_NS above), in which case nftw() shall return -1 and
108 set errno to indicate the error.
109 * The tree is exhausted, in which case nftw() shall return 0.
111
113 The nftw() function shall fail if:
114 EACCES Search permission is denied for any component of path or read
116 permission is denied for path, or fn returns -1 and does not
117 reset errno.
118 ELOOP A loop exists in symbolic links encountered during resolution of
120 the path argument.
121 ENAMETOOLONG
123 The length of a component of a pathname is longer than
124 {NAME_MAX}.
125 ENOENT A component of path does not name an existing file or path is an
127 empty string.
128 ENOTDIR
130 A component of path names an existing file that is neither a
131 directory nor a symbolic link to a directory.
132 EOVERFLOW
134 A field in the stat structure cannot be represented correctly in
135 the current programming environment for one or more files found
136 in the file hierarchy.
137 The nftw() function may fail if:
139 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
141 resolution of the path argument.
142 EMFILE All file descriptors available to the process are currently
144 open.
145 ENAMETOOLONG
147 The length of a pathname exceeds {PATH_MAX}, or pathname resolu‐
148 tion of a symbolic link produced an intermediate result with a
149 length that exceeds {PATH_MAX}.
150 ENFILE Too many files are currently open in the system.
152 In addition, errno may be set if the function pointed to by fn causes
154 errno to be set.
155 The following sections are informative.
157
159 The following program traverses the directory tree under the path named
160 in its first command-line argument, or under the current directory if
161 no argument is supplied. It displays various information about each
162 file. The second command-line argument can be used to specify charac‐
163 ters that control the value assigned to the flags argument when calling
164 nftw().
165 #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.1‐2017, <ftw.h>
230
232 Portions of this text are reprinted and reproduced in electronic form
233 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
234 table Operating System Interface (POSIX), The Open Group Base Specifi‐
235 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
236 Electrical and Electronics Engineers, Inc and The Open Group. In the
237 event of any discrepancy between this version and the original IEEE and
238 The Open Group Standard, the original IEEE and The Open Group Standard
239 is the referee document. The original Standard can be obtained online
240 at http://www.opengroup.org/unix/online.html .
241 Any typographical or formatting errors that appear in this page are
243 most likely to have been introduced during the conversion of the source
244 files to man page format. To report such errors, see https://www.ker‐
245 nel.org/doc/man-pages/reporting_bugs.html .
246IEEE/The Open Group 2017 NFTW(3P)