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
12 dirname - report the parent directory name of a file pathname
13
15 #include <libgen.h>
16 char *dirname(char *path);
18
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 reentrant. A function that is not
31 required to be reentrant is not required to be thread-safe.
32
34 The dirname() function shall return a pointer to a string that is the
35 parent directory of path. If path is a null pointer or points to an
36 empty string, a pointer to a string "." is returned.
37 The dirname() function may modify the string pointed to by path, and
39 may return a pointer to static storage that may then be overwritten by
40 subsequent calls to 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[PATH_MAX], *pathcopy;
53 int fd;
54 fgets(path, PATH_MAX, stdin);
55 pathcopy = strdup(path);
56 chdir(dirname(pathcopy));
57 fd = open(basename(path), O_RDONLY);
58 Sample Input and Output Strings for dirname()
60 In the following table, the input string is the value pointed to by
61 path, and the output string is the return value of the dirname() func‐
62 tion.
63 Input String Output String
65 "/usr/lib" "/usr"
66 "/usr/" "/"
68 "usr" "."
69 "/" "/"
70 "." "."
71 ".." "."
72 Changing the Current Directory to the Parent Directory
74 The following program fragment reads a pathname, changes the current
75 working directory to the parent directory, and opens the file.
76 #include <unistd.h>
79 #include <limits.h>
80 #include <stdio.h>
81 #include <fcntl.h>
82 #include <string.h>
83 #include <libgen.h>
84 ...
85 char path[PATH_MAX], *pathcopy;
86 int fd;
87 ...
88 fgets(path, PATH_MAX, stdin);
89 pathcopy = strdup(path);
90 chdir(dirname(pathcopy));
91 fd = open(basename(path), O_RDONLY);
92
94 The dirname() and basename() functions together yield a complete path‐
95 name. The expression dirname(path) obtains the pathname of the direc‐
96 tory where basename(path) is found.
97 Since the meaning of the leading "//" is implementation-defined,
99 dirname(" //foo) may return either "//" or '/' (but nothing else).
100
102 None.
103
105 None.
106
108 basename(), the Base Definitions volume of IEEE Std 1003.1-2001, <lib‐
109 gen.h>
110
112 Portions of this text are reprinted and reproduced in electronic form
113 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
114 -- Portable Operating System Interface (POSIX), The Open Group Base
115 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
116 Electrical and Electronics Engineers, Inc and The Open Group. In the
117 event of any discrepancy between this version and the original IEEE and
118 The Open Group Standard, the original IEEE and The Open Group Standard
119 is the referee document. The original Standard can be obtained online
120 at http://www.opengroup.org/unix/online.html .
121IEEE/The Open Group 2003 DIRNAME(3P)