dirname man page

Prolog

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

Synopsis

#include <libgen.h>

char *dirname(char *path);

Description

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 ".". If path is a null pointer or points to an empty string, dirname() shall return a pointer to the string ".".

The dirname() function need not be thread-safe.

Return Value

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 "." 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().

Errors

No errors are defined.

The following sections are informative.

Examples

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 StringOutput String
"/usr/lib""/usr"
"/usr/""/"
"usr""."
"/""/"
".""."
"..""."

Application Usage

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 "//" is implementation-defined, dirname("//foo) may return either "//" or '/' (but nothing else).

See Also

basename()

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

Info

2013 IEEE/The Open Group POSIX Programmer's Manual