1NFTW(P) POSIX Programmer's Manual NFTW(P)
2
6 nftw - walk a file tree
7
9 #include <ftw.h>
10 int nftw(const char *path, int (*fn)(const char *,
12 const struct stat *, int, struct FTW *), int depth, int flags);
13
16 The nftw() function shall recursively descend the directory hierarchy
17 rooted in path. The nftw() function has a similar effect to ftw()
18 except that it takes an additional argument flags, which is a bitwise-
19 inclusive OR of zero or more of the following flags:
20 FTW_CHDIR
22 If set, nftw() shall change the current working directory to
23 each directory as it reports files in that directory. If clear,
24 nftw() shall not change the current working directory.
25 FTW_DEPTH
27 If set, nftw() shall report all files in a directory before
28 reporting the directory itself. If clear, nftw() shall report
29 any directory before reporting the files in that directory.
30 FTW_MOUNT
32 If set, nftw() shall only report files in the same file system
33 as path. If clear, nftw() shall report all files encountered
34 during the walk.
35 FTW_PHYS
37 If set, nftw() shall perform a physical walk and shall not fol‐
38 low symbolic links.
39 If FTW_PHYS is clear and FTW_DEPTH is set, nftw() shall follow links
42 instead of reporting them, but shall not report any directory that
43 would be a descendant of itself. If FTW_PHYS is clear and FTW_DEPTH is
44 clear, nftw() shall follow links instead of reporting them, but shall
45 not report the contents of any directory that would be a descendant of
46 itself.
47 At each file it encounters, nftw() shall call the user-supplied func‐
49 tion fn with four arguments:
50 * The first argument is the pathname of the object.
52 * The second argument is a pointer to the stat buffer containing
54 information on the object.
55 * The third argument is an integer giving additional information. Its
57 value is one of the following:
58 FTW_F
60 The object is a file.
61 FTW_D
63 The object is a directory.
64 FTW_DP
66 The object is a directory and subdirectories have been visited.
67 (This condition shall only occur if the FTW_DEPTH flag is
68 included in flags.)
69 FTW_SL
71 The object is a symbolic link. (This condition shall only occur
72 if the FTW_PHYS flag is included in flags.)
73 FTW_SLN
75 The object is a symbolic link that does not name an existing
76 file. (This condition shall only occur if the FTW_PHYS flag is
77 not included in flags.)
78 FTW_DNR
80 The object is a directory that cannot be read. The fn function
81 shall not be called for any of its descendants.
82 FTW_NS
84 The stat() function failed on the object because of lack of
85 appropriate permission. The stat buffer passed to fn is unde‐
86 fined. Failure of stat() for any other reason is considered an
87 error and nftw() shall return -1.
88 * The fourth argument is a pointer to an FTW structure. The value of
91 base is the offset of the object's filename in the pathname passed
92 as the first argument to fn. The value of level indicates depth rel‐
93 ative to the root of the walk, where the root level is 0.
94 The results are unspecified if the application-supplied fn function
96 does not preserve the current working directory.
97 The argument depth sets the maximum number of file descriptors that
99 shall be used by nftw() while traversing the file tree. At most one
100 file descriptor shall be used for each directory level.
101 The nftw() function need not be reentrant. A function that is not
103 required to be reentrant is not required to be thread-safe.
104
106 The nftw() function shall continue until the first of the following
107 conditions occurs:
108 * An invocation of fn shall return a non-zero value, in which case
110 nftw() shall return that value.
111 * The nftw() function detects an error other than [EACCES] (see
113 FTW_DNR and FTW_NS above), in which case nftw() shall return -1 and
114 set errno to indicate the error.
115 * The tree is exhausted, in which case nftw() shall return 0.
117
119 The nftw() function shall fail if:
120 EACCES Search permission is denied for any component of path or read
122 permission is denied for path, or fn returns -1 and does not
123 reset errno.
124 ELOOP A loop exists in symbolic links encountered during resolution of
126 the path argument.
127 ENAMETOOLONG
129 The length of the path argument exceeds {PATH_MAX} or a pathname
130 component is longer than {NAME_MAX}.
131 ENOENT A component of path does not name an existing file or path is an
133 empty string.
134 ENOTDIR
136 A component of path is not a directory.
137 EOVERFLOW
139 A field in the stat structure cannot be represented correctly in
140 the current programming environment for one or more files found
141 in the file hierarchy.
142 The nftw() function may fail if:
145 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
147 resolution of the path argument.
148 EMFILE {OPEN_MAX} file descriptors are currently open in the calling
150 process.
151 ENAMETOOLONG
153 Pathname resolution of a symbolic link produced an intermediate
154 result whose length exceeds {PATH_MAX}.
155 ENFILE Too many files are currently open in the system.
157 In addition, errno may be set if the function pointed to by fn causes
160 errno to be set.
161 The following sections are informative.
163
165 The following example walks the /tmp directory and its subdirectories,
166 calling the nftw() function for every directory entry, to a maximum of
167 5 levels deep.
168 #include <ftw.h>
171 ...
172 int nftwfunc(const char *, const struct stat *, int, struct FTW *);
173 int nftwfunc(const char *filename, const struct stat *statptr,
176 int fileflags, struct FTW *pfwt)
177 {
178 return 0;
179 }
180 ...
181 char *startpath = "/tmp";
182 int depth = 5;
183 int flags = FTW_CHDIR | FTW_DEPTH | FTW_MOUNT;
184 int ret;
185 ret = nftw(startpath, nftwfunc, depth, flags);
188
190 None.
191
193 None.
194
196 None.
197
199 lstat() , opendir() , readdir() , stat() , the Base Definitions volume
200 of IEEE Std 1003.1-2001, <ftw.h>
201
203 Portions of this text are reprinted and reproduced in electronic form
204 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
205 -- Portable Operating System Interface (POSIX), The Open Group Base
206 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
207 Electrical and Electronics Engineers, Inc and The Open Group. In the
208 event of any discrepancy between this version and the original IEEE and
209 The Open Group Standard, the original IEEE and The Open Group Standard
210 is the referee document. The original Standard can be obtained online
211 at http://www.opengroup.org/unix/online.html .
212IEEE/The Open Group 2003 NFTW(P)