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Linux kernel and C library user-space interface documentation


POSIX Manual Pages


This manual page is part of the POSIX Programmer’s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.


dirname — report the parent directory name of a file pathname


#include <libgen.h>

char *dirname(char *path);


The dirname() function shall take a pointer to a character string that contains a pathname, and return a pointer to a string that is a pathname of the parent directory of that file. Trailing ’/’ characters in the path are not counted as part of the path.
If path does not contain a ’/’, then dirname() shall return a pointer to the string \(dq.\(dq. If path is a null pointer or points to an empty string, dirname() shall return a pointer to the string \(dq.\(dq.
The dirname() function need not be thread-safe.


The dirname() function shall return a pointer to a string that is the parent directory of path. If path is a null pointer or points to an empty string, a pointer to a string \(dq.\(dq is returned.
The dirname() function may modify the string pointed to by path, and may return a pointer to internal storage. The returned pointer might be invalidated or the storage might be overwritten by a subsequent call to dirname().


No errors are defined.
The following sections are informative.


The following code fragment reads a pathname, changes the current working directory to the parent directory, and opens the file.

char *path = NULL, *pathcopy;
size_t buflen = 0;
ssize_t linelen = 0;
int fd;

linelen = getline(&path, &buflen, stdin);
path[linelen-1] = 0; pathcopy = strdup(path); if (chdir(dirname(pathcopy)) < 0) { ... } if ((fd = open(basename(path), O_RDONLY)) >= 0) { ... close (fd); } ... free (pathcopy); free (path);

Sample Input and Output Strings for dirname()

In the following table, the input string is the value pointed to by path, and the output string is the return value of the dirname() function.
Input String Output String
"/usr/lib" "/usr"
"/usr/" "/"
"usr" "."
"/" "/"
"." "."
".." "."


The dirname() and basename() functions together yield a complete pathname. The expression dirname(path) obtains the pathname of the directory where basename(path) is found.
Since the meaning of the leading \(dq//\(dq is implementation-defined, dirname( //foo) may return either \(dq//\(dq or ’/’ (but nothing else).






The Base Definitions volume of POSIX.1-2008, <libgen.h>


Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at .
Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see .
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