1DIRNAME(P) POSIX Programmer's Manual DIRNAME(P)
2
6 dirname - report the parent directory name of a file pathname
7
9 #include <libgen.h>
10 char *dirname(char *path);
12
15 The dirname() function shall take a pointer to a character string that
16 contains a pathname, and return a pointer to a string that is a path‐
17 name of the parent directory of that file. Trailing '/' characters in
18 the path are not counted as part of the path.
19 If path does not contain a '/' , then dirname() shall return a pointer
21 to the string "." . If path is a null pointer or points to an empty
22 string, dirname() shall return a pointer to the string "." .
23 The dirname() function need not be reentrant. A function that is not
25 required to be reentrant is not required to be thread-safe.
26
28 The dirname() function shall return a pointer to a string that is the
29 parent directory of path. If path is a null pointer or points to an
30 empty string, a pointer to a string "." is returned.
31 The dirname() function may modify the string pointed to by path, and
33 may return a pointer to static storage that may then be overwritten by
34 subsequent calls to dirname().
35
37 No errors are defined.
38 The following sections are informative.
40
42 The following code fragment reads a pathname, changes the current work‐
43 ing directory to the parent directory, and opens the file.
44 char path[PATH_MAX], *pathcopy;
47 int fd;
48 fgets(path, PATH_MAX, stdin);
49 pathcopy = strdup(path);
50 chdir(dirname(pathcopy));
51 fd = open(basename(path), O_RDONLY);
52 Sample Input and Output Strings for dirname()
54 In the following table, the input string is the value pointed to by
55 path, and the output string is the return value of the dirname() func‐
56 tion.
57 Input String Output String
59 "/usr/lib" "/usr"
60 "/usr/" "/"
61 "usr" "."
62 "/" "/"
63 "." "."
64 ".." "."
65 Changing the Current Directory to the Parent Directory
67 The following program fragment reads a pathname, changes the current
68 working directory to the parent directory, and opens the file.
69 #include <unistd.h>
72 #include <limits.h>
73 #include <stdio.h>
74 #include <fcntl.h>
75 #include <string.h>
76 #include <libgen.h>
77 ...
78 char path[PATH_MAX], *pathcopy;
79 int fd;
80 ...
81 fgets(path, PATH_MAX, stdin);
82 pathcopy = strdup(path);
83 chdir(dirname(pathcopy));
84 fd = open(basename(path), O_RDONLY);
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() , the Base Definitions volume of IEEE Std 1003.1-2001, <lib‐
102 gen.h>
103
105 Portions of this text are reprinted and reproduced in electronic form
106 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
107 -- Portable Operating System Interface (POSIX), The Open Group Base
108 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
109 Electrical and Electronics Engineers, Inc and The Open Group. In the
110 event of any discrepancy between this version and the original IEEE and
111 The Open Group Standard, the original IEEE and The Open Group Standard
112 is the referee document. The original Standard can be obtained online
113 at http://www.opengroup.org/unix/online.html .
114IEEE/The Open Group 2003 DIRNAME(P)