This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       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.

       Default.

       Default.

       Thefollowingsectionsareinformative.

       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 .

IEEE/The Open Group                                   2017                                       DIRNAME(1POSIX)

       The  string  operand  shall  be  treated  as  a  pathname,  as  defined in the Base Definitions volume of
       POSIX.1‐2017, Section3.271, 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.

       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.1‐2017, Section8.2, InternationalizationVariables 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.

       The EXAMPLES section of the basename() function  (see  the  System  Interfaces  volume  of  POSIX.1‐2017,
       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.

       See also the examples for the basename utility.

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

       None.

       None.

       None.

       dirname — return the directory portion of a pathname

       The following operand shall be supported:

       string    A string.

       None.

       None.

       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.

       The behaviors of basename and dirname in this volume of POSIX.1‐2017 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.1‐2017, Section3.271, Pathname allows  trailing  <slash>  characters.  The  basename  and  dirname
       utilities have to specify consistent handling for all valid pathnames.

Section2.5, ParametersandVariables, basename

       The Base Definitions volume of POSIX.1‐2017, Section3.271, Pathname, Chapter8, EnvironmentVariables

       The System Interfaces volume of POSIX.1‐2017, basename(), dirname()

       The standard error shall be used only for diagnostic messages.

       Not used.

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

           "%s\n", <resultingstring>

       dirname string