DIRNAME(3POSIX)

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.

NAME
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. 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.

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);

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()

The Base Definitions volume of POSIX.1-2017, <libgen.h>

The Shell and Utilities volume of POSIX.1-2017, basename, dirname

COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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 http://www.opengroup.org/unix/online.html .

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 https://www.kernel.org/doc/man-pages/reporting_bugs.html .