1FTW(3P) POSIX Programmer's Manual FTW(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 ftw — traverse (walk) a file tree
13
15 #include <ftw.h>
16 int ftw(const char *path, int (*fn)(const char *,
18 const struct stat *ptr, int flag), int ndirs);
19
21 The ftw() function shall recursively descend the directory hierarchy
22 rooted in path. For each object in the hierarchy, ftw() shall call the
23 function pointed to by fn, passing it a pointer to a null-terminated
24 character string containing the name of the object, a pointer to a stat
25 structure containing information about the object, filled in as if
26 stat() or lstat() had been called to retrieve the information. Possible
27 values of the integer, defined in the <ftw.h> header, are:
28 FTW_D For a directory.
30 FTW_DNR For a directory that cannot be read.
32 FTW_F For a non-directory file.
34 FTW_SL For a symbolic link (but see also FTW_NS below).
36 FTW_NS For an object other than a symbolic link on which stat()
38 could not successfully be executed. If the object is a sym‐
39 bolic link and stat() failed, it is unspecified whether ftw()
40 passes FTW_SL or FTW_NS to the user-supplied function.
41 If the integer is FTW_DNR, descendants of that directory shall not be
43 processed. If the integer is FTW_NS, the stat structure contains unde‐
44 fined values. An example of an object that would cause FTW_NS to be
45 passed to the function pointed to by fn would be a file in a directory
46 with read but without execute (search) permission.
47 The ftw() function shall visit a directory before visiting any of its
49 descendants.
50 The ftw() function shall use at most one file descriptor for each level
52 in the tree.
53 The argument ndirs should be in the range [1,{OPEN_MAX}].
55 The tree traversal shall continue until either the tree is exhausted,
57 an invocation of fn returns a non-zero value, or some error, other than
58 [EACCES], is detected within ftw().
59 The ndirs argument shall specify the maximum number of directory
61 streams or file descriptors or both available for use by ftw() while
62 traversing the tree. When ftw() returns it shall close any directory
63 streams and file descriptors it uses not counting any opened by the
64 application-supplied fn function.
65 The results are unspecified if the application-supplied fn function
67 does not preserve the current working directory.
68 The ftw() function need not be thread-safe.
70
72 If the tree is exhausted, ftw() shall return 0. If the function pointed
73 to by fn returns a non-zero value, ftw() shall stop its tree traversal
74 and return whatever value was returned by the function pointed to by
75 fn. If ftw() detects an error, it shall return -1 and set errno to
76 indicate the error.
77 If ftw() encounters an error other than [EACCES] (see FTW_DNR and
79 FTW_NS above), it shall return -1 and set errno to indicate the error.
80 The external variable errno may contain any error value that is possi‐
81 ble when a directory is opened or when one of the stat functions is
82 executed on a directory or file.
83
85 The ftw() function shall fail if:
86 EACCES Search permission is denied for any component of path or read
88 permission is denied for path.
89 ELOOP A loop exists in symbolic links encountered during resolution of
91 the path argument.
92 ENAMETOOLONG
94 The length of a component of a pathname is longer than
95 {NAME_MAX}.
96 ENOENT A component of path does not name an existing file or path is an
98 empty string.
99 ENOTDIR
101 A component of path names an existing file that is neither a
102 directory nor a symbolic link to a directory.
103 EOVERFLOW
105 A field in the stat structure cannot be represented correctly in
106 the current programming environment for one or more files found
107 in the file hierarchy.
108 The ftw() function may fail if:
110 EINVAL The value of the ndirs argument is invalid.
112 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
114 resolution of the path argument.
115 ENAMETOOLONG
117 The length of a pathname exceeds {PATH_MAX}, or pathname resolu‐
118 tion of a symbolic link produced an intermediate result with a
119 length that exceeds {PATH_MAX}.
120 In addition, if the function pointed to by fn encounters system errors,
122 errno may be set accordingly.
123 The following sections are informative.
125
127 Walking a Directory Structure
128 The following example walks the current directory structure, calling
129 the fn function for every directory entry, using at most 10 file
130 descriptors:
131 #include <ftw.h>
134 ...
135 if (ftw(".", fn, 10) != 0) {
136 perror("ftw"); exit(2);
137 }
138
140 The ftw() function may allocate dynamic storage during its operation.
141 If ftw() is forcibly terminated, such as by longjmp() or siglongjmp()
142 being executed by the function pointed to by fn or an interrupt rou‐
143 tine, ftw() does not have a chance to free that storage, so it remains
144 permanently allocated. A safe way to handle interrupts is to store the
145 fact that an interrupt has occurred, and arrange to have the function
146 pointed to by fn return a non-zero value at its next invocation.
147 Applications should use the nftw() function instead of the obsolescent
149 ftw() function.
150
152 None.
153
155 The ftw() function may be removed in a future version.
156
158 fdopendir(), fstatat(), longjmp(), nftw(), siglongjmp()
159 The Base Definitions volume of POSIX.1‐2017, <ftw.h>, <sys_stat.h>
161
163 Portions of this text are reprinted and reproduced in electronic form
164 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
165 table Operating System Interface (POSIX), The Open Group Base Specifi‐
166 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
167 Electrical and Electronics Engineers, Inc and The Open Group. In the
168 event of any discrepancy between this version and the original IEEE and
169 The Open Group Standard, the original IEEE and The Open Group Standard
170 is the referee document. The original Standard can be obtained online
171 at http://www.opengroup.org/unix/online.html .
172 Any typographical or formatting errors that appear in this page are
174 most likely to have been introduced during the conversion of the source
175 files to man page format. To report such errors, see https://www.ker‐
176 nel.org/doc/man-pages/reporting_bugs.html .
177IEEE/The Open Group 2017 FTW(3P)