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
22 The ftw() function shall recursively descend the directory hierarchy
23 rooted in path. For each object in the hierarchy, ftw() shall call the
24 function pointed to by fn, passing it a pointer to a null-terminated
25 character string containing the name of the object, a pointer to a stat
26 structure containing information about the object, and an integer.
27 Possible values of the integer, defined in the <ftw.h> header, are:
28 FTW_D For a directory.
30 FTW_DNR
32 For a directory that cannot be read.
33 FTW_F For a file.
35 FTW_SL For a symbolic link (but see also FTW_NS below).
37 FTW_NS For an object other than a symbolic link on which stat() could
39 not successfully be executed. If the object is a symbolic link
40 and stat() failed, it is unspecified whether ftw() passes FTW_SL
41 or FTW_NS to the user-supplied function.
42 If the integer is FTW_DNR, descendants of that directory shall not be
45 processed. If the integer is FTW_NS, the stat structure contains unde‐
46 fined values. An example of an object that would cause FTW_NS to be
47 passed to the function pointed to by fn would be a file in a directory
48 with read but without execute (search) permission.
49 The ftw() function shall visit a directory before visiting any of its
51 descendants.
52 The ftw() function shall use at most one file descriptor for each level
54 in the tree.
55 The argument ndirs should be in the range [1, {OPEN_MAX}].
57 The tree traversal shall continue until either the tree is exhausted,
59 an invocation of fn returns a non-zero value, or some error, other than
60 [EACCES], is detected within ftw().
61 The ndirs argument shall specify the maximum number of directory
63 streams or file descriptors or both available for use by ftw() while
64 traversing the tree. When ftw() returns it shall close any directory
65 streams and file descriptors it uses not counting any opened by the
66 application-supplied fn function.
67 The results are unspecified if the application-supplied fn function
69 does not preserve the current working directory.
70 The ftw() function need not be reentrant. A function that is not
72 required to be reentrant is not required to be thread-safe.
73
75 If the tree is exhausted, ftw() shall return 0. If the function pointed
76 to by fn returns a non-zero value, ftw() shall stop its tree traversal
77 and return whatever value was returned by the function pointed to by
78 fn. If ftw() detects an error, it shall return -1 and set errno to
79 indicate the error.
80 If ftw() encounters an error other than [EACCES] (see FTW_DNR and
82 FTW_NS above), it shall return -1 and set errno to indicate the error.
83 The external variable errno may contain any error value that is possi‐
84 ble when a directory is opened or when one of the stat functions is
85 executed on a directory or file.
86
88 The ftw() function shall fail if:
89 EACCES Search permission is denied for any component of path or read
91 permission is denied for path.
92 ELOOP A loop exists in symbolic links encountered during resolution of
94 the path argument.
95 ENAMETOOLONG
97 The length of the path argument exceeds {PATH_MAX} or a pathname
98 component is longer than {NAME_MAX}.
99 ENOENT A component of path does not name an existing file or path is an
101 empty string.
102 ENOTDIR
104 A component of path is not a directory.
105 EOVERFLOW
107 A field in the stat structure cannot be represented correctly in
108 the current programming environment for one or more files found
109 in the file hierarchy.
110 The ftw() function may fail if:
113 EINVAL The value of the ndirs argument is invalid.
115 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
117 resolution of the path argument.
118 ENAMETOOLONG
120 Pathname resolution of a symbolic link produced an intermediate
121 result whose length exceeds {PATH_MAX}.
122 In addition, if the function pointed to by fn encounters system errors,
125 errno may be set accordingly.
126 The following sections are informative.
128
130 Walking a Directory Structure
131 The following example walks the current directory structure, calling
132 the fn function for every directory entry, using at most 10 file
133 descriptors:
134 #include <ftw.h>
137 ...
138 if (ftw(".", fn, 10) != 0) {
139 perror("ftw"); exit(2);
140 }
141
143 The ftw() function may allocate dynamic storage during its operation.
144 If ftw() is forcibly terminated, such as by longjmp() or siglongjmp()
145 being executed by the function pointed to by fn or an interrupt rou‐
146 tine, ftw() does not have a chance to free that storage, so it remains
147 permanently allocated. A safe way to handle interrupts is to store the
148 fact that an interrupt has occurred, and arrange to have the function
149 pointed to by fn return a non-zero value at its next invocation.
150
152 None.
153
155 None.
156
158 longjmp(), lstat(), malloc(), nftw(), opendir(), siglongjmp(), stat(),
159 the Base Definitions volume of IEEE Std 1003.1-2001, <ftw.h>,
160 <sys/stat.h>
161
163 Portions of this text are reprinted and reproduced in electronic form
164 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
165 -- Portable Operating System Interface (POSIX), The Open Group Base
166 Specifications Issue 6, Copyright (C) 2001-2003 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 .
172IEEE/The Open Group 2003 FTW(3P)