1DIRNAME(3P) POSIX Programmer's Manual DIRNAME(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 dirname — report the parent directory name of a file pathname
14
16 #include <libgen.h>
17 char *dirname(char *path);
19
21 The dirname() function shall take a pointer to a character string that
22 contains a pathname, and return a pointer to a string that is a path‐
23 name of the parent directory of that file. Trailing '/' characters in
24 the path are not counted as part of the path.
25 If path does not contain a '/', then dirname() shall return a pointer
27 to the string ".". If path is a null pointer or points to an empty
28 string, dirname() shall return a pointer to the string ".".
29 The dirname() function need not be thread-safe.
31
33 The dirname() function shall return a pointer to a string that is the
34 parent directory of path. If path is a null pointer or points to an
35 empty string, a pointer to a string "." is returned.
36 The dirname() function may modify the string pointed to by path, and
38 may return a pointer to internal storage. The returned pointer might be
39 invalidated or the storage might be overwritten by a subsequent call to
40 dirname().
41
43 No errors are defined.
44 The following sections are informative.
46
48 The following code fragment reads a pathname, changes the current work‐
49 ing directory to the parent directory, and opens the file.
50 char *path = NULL, *pathcopy;
52 size_t buflen = 0;
53 ssize_t linelen = 0;
54 int fd;
55 linelen = getline(&path, &buflen, stdin);
57 path[linelen-1] = 0;
59 pathcopy = strdup(path);
60 if (chdir(dirname(pathcopy)) < 0) {
61 ...
62 }
63 if ((fd = open(basename(path), O_RDONLY)) >= 0) {
64 ...
65 close (fd);
66 }
67 ...
68 free (pathcopy);
69 free (path);
70 Sample Input and Output Strings for dirname()
72 In the following table, the input string is the value pointed to by
73 path, and the output string is the return value of the dirname() func‐
74 tion.
75 ┌─────────────┬───────────────┐
77 │Input String │ Output String │
78 ├─────────────┼───────────────┤
79 │"/usr/lib" │ "/usr" │
80 │"/usr/" │ "/" │
81 │"usr" │ "." │
82 │"/" │ "/" │
83 │"." │ "." │
84 │".." │ "." │
85 └─────────────┴───────────────┘
87 The dirname() and basename() functions together yield a complete path‐
88 name. The expression dirname(path) obtains the pathname of the direc‐
89 tory where basename(path) is found.
90 Since the meaning of the leading "//" is implementation-defined,
92 dirname("//foo) may return either "//" or '/' (but nothing else).
93
95 None.
96
98 None.
99
101 basename()
102 The Base Definitions volume of POSIX.1‐2008, <libgen.h>
104
106 Portions of this text are reprinted and reproduced in electronic form
107 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
108 -- Portable Operating System Interface (POSIX), The Open Group Base
109 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
110 cal and Electronics Engineers, Inc and The Open Group. (This is
111 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
112 event of any discrepancy between this version and the original IEEE and
113 The Open Group Standard, the original IEEE and The Open Group Standard
114 is the referee document. The original Standard can be obtained online
115 at http://www.unix.org/online.html .
116 Any typographical or formatting errors that appear in this page are
118 most likely to have been introduced during the conversion of the source
119 files to man page format. To report such errors, see https://www.ker‐
120 nel.org/doc/man-pages/reporting_bugs.html .
121IEEE/The Open Group 2013 DIRNAME(3P)