DIRNAME(1P)                                         POSIX Programmer's Manual                                        DIRNAME(1P)



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

NAME
       dirname - return the directory portion of a pathname

SYNOPSIS
       dirname string

DESCRIPTION
       The  string  operand  shall  be treated as a pathname, as defined in the Base Definitions volume of IEEE Std 1003.1-2001,
       Section 3.266, Pathname. The string string shall be converted to the name of the directory containing the filename corre-
       sponding to the last pathname component in string, performing actions equivalent to the following steps in order:

        1. If string is //, skip steps 2 to 5.

        2. If  string consists entirely of slash characters, string shall be set to a single slash character. In this case, skip
           steps 3 to 8.

        3. If there are any trailing slash characters in string, they shall be removed.

        4. If there are no slash characters remaining in string, string shall be set to a single period character. In this case,
           skip steps 5 to 8.

        5. If there are any trailing non-slash characters in string, they shall be removed.

        6. If the remaining string is //, it is implementation-defined whether steps 7 and 8 are skipped or processed.

        7. If there are any trailing slash characters in string, they shall be removed.

        8. If the remaining string is empty, string shall be set to a single slash character.

       The resulting string shall be written to standard output.

OPTIONS
       None.

OPERANDS
       The following operand shall be supported:

       string A string.


STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of dirname:

       LANG   Provide  a  default value for the internationalization variables that are unset or null. (See the Base Definitions
              volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the precedence  of  international-
              ization variables used to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.

       LC_CTYPE
              Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-
              byte as opposed to multi-byte characters in arguments).

       LC_MESSAGES
              Determine the locale that should be used to affect the format and contents of diagnostic messages written to stan-
              dard error.

       NLSPATH
              Determine the location of message catalogs for the processing of LC_MESSAGES .


ASYNCHRONOUS EVENTS
       Default.

STDOUT
       The dirname utility shall write a line to the standard output in the following format:


              "%s\n", <resulting string>

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0     Successful completion.

       >0     An error occurred.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       The  definition  of  pathname specifies implementation-defined behavior for pathnames starting with two slash characters.
       Therefore, applications shall not arbitrarily add slashes to the beginning of a pathname  unless  they  can  ensure  that
       there are more or less than two or are prepared to deal with the implementation-defined consequences.

EXAMPLES
                                                    Command            Results
                                                    dirname /          /
                                                    dirname //         / or //
                                                    dirname /a/b/      /a
                                                    dirname //a//b//   //a
                                                    dirname            Unspecified
                                                    dirname a          . ($? = 0)
                                                    dirname ""         . ($? = 0)
                                                    dirname /a         /
                                                    dirname /a/b       /a
                                                    dirname a/b        a

RATIONALE
       The  dirname utility originated in System III. It has evolved through the System V releases to a version that matches the
       requirements specified in this description in System V Release 3.  4.3 BSD and earlier versions did not include dirname.

       The behaviors of basename and dirname in this volume of IEEE Std 1003.1-2001 have been coordinated so that when string is
       a valid pathname:


              $(basename "string")

       would be a valid filename for the file in the directory:


              $(dirname "string")

       This  would not work for the versions of these utilities in early proposals due to the way processing of trailing slashes
       was specified. Consideration was given to leaving processing unspecified if there were trailing slashes, but this  cannot
       be  done; the Base Definitions volume of IEEE Std 1003.1-2001, Section 3.266, Pathname allows trailing slashes. The base-
       name and dirname utilities have to specify consistent handling for all valid pathnames.

FUTURE DIRECTIONS
       None.

SEE ALSO
       basename(), Parameters and Variables

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   DIRNAME(1P)