xenial (1) dirname.1posix.gz

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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 — 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
       POSIX.1‐2008, Section 3.267, Pathname.  The string string shall be converted to the name of the directory
       containing  the  filename  corresponding  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 POSIX.1‐2008, Section 8.2, Internationalization  Variables  for  the
                 precedence   of   internationalization  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 standard 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 <slash> characters 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

                                           ┌─────────────────┬─────────────┐
                                           │    CommandResults   │
                                           ├─────────────────┼─────────────┤
                                           │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/ba           │
                                           └─────────────────┴─────────────┘
       See also the examples for the basename utility.

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 POSIX.1‐2008 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 <slash> characters was specified. Consideration was given to leaving processing  unspecified  if
       there  were  trailing  <slash>  characters,  but  this  cannot  be  done;  the Base Definitions volume of
       POSIX.1‐2008, Section 3.267, Pathname allows  trailing  <slash>  characters.  The  basename  and  dirname
       utilities have to specify consistent handling for all valid pathnames.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Section 2.5, Parameters and Variables, basename

       The Base Definitions volume of POSIX.1‐2008, Section 3.267, Pathname, Chapter 8, Environment Variables

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications  Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
       and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .

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