Manpages - dirname.3p

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. 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.

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.

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);

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.

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).

None.

None.

/basename ( )/

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

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

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 .

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