NAME

dirname - report the parent directory name of a file pathname

SYNOPSIS

[XSI] #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. The dirname() function shall not perform pathname resolution; the result shall not be affected by whether or not path exists or by its file type. Trailing '/' characters in the path that are not also leading '/' characters shall not be 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 may modify the string pointed to by path, and may return a pointer to static storage that may then be overwritten by a subsequent call to dirname().

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

RETURN VALUE

The dirname() function shall return a pointer to a string as described above.

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(). The returned pointer might also be invalidated if the calling thread is terminated.

ERRORS

No errors are defined.

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);

The EXAMPLES section of the basename() function (see basename) includes a table showing examples of the results of processing several sample pathnames by the basename() and dirname() functions and by the basename and dirname utilities.

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).

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

basename

XBD <libgen.h>

XCU basename, dirname

CHANGE HISTORY

First released in Issue 4, Version 2.

Issue 5

Moved from X/OPEN UNIX extension to BASE.

Normative text previously in the APPLICATION USAGE section is moved to the DESCRIPTION.

A note indicating that this function need not be reentrant is added to the DESCRIPTION.

Issue 7

Austin Group Interpretation 1003.1-2001 #156 is applied.

The EXAMPLES section is revised.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0068 [75] is applied.

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0077 [830], XSH/TC2-2008/0078 [612], XSH/TC2-2008/0079 [830], XSH/TC2-2008/0080 [656], and XSH/TC2-2008/0081 [612] are applied.