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       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

       basename — return non-directory portion of a pathname

SYNOPSIS

       basename string [suffix]

DESCRIPTION

The string operand shall be treated as a pathname, as defined in the Base Definitions
volume of POSIX.1‐2017, Section 3.271, Pathname. The string string shall be converted to
the filename corresponding to the last pathname component in string and then the suffix
string suffix, if present, shall be removed. This shall be done by performing actions
equivalent to the following steps in order:

1. If string is a null string, it is unspecified whether the resulting string is '.' or
a null string. In either case, skip steps 2 through 6.

2. If string is "//", it is implementation-defined whether steps 3 to 6 are skipped or
processed.

3. If string consists entirely of <slash> characters, string shall be set to a single
<slash> character. In this case, skip steps 4 to 6.

4. If there are any trailing <slash> characters in string, they shall be removed.

5. If there are any <slash> characters remaining in string, the prefix of string up to
and including the last <slash> character in string shall be removed.

6. If the suffix operand is present, is not identical to the characters remaining in
string, and is identical to a suffix of the characters remaining in string, the suffix
suffix shall be removed from string. Otherwise, string is not modified by this step.
It shall not be considered an error if suffix is not found in string.

The resulting string shall be written to standard output.

OPTIONS

       None.

OPERANDS

       The following operands shall be supported:

       string    A string.

       suffix    A string.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of basename:

       LANG      Provide a default value for the internationalization variables that are unset or
                 null.   (See   the   Base  Definitions  volume  of  POSIX.1‐2017,  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 basename 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

       If the string string is a valid pathname:

           $(basename -- "string")

       produces  a  filename that could be used to open the file named by string in the directory
       returned by:

           $(dirname -- "string")

       If the string string is not a valid pathname, the same algorithm is used, but  the  result
       need  not be a valid filename. The basename utility is not expected to make any judgements
       about the validity of string as a pathname; it just follows  the  specified  algorithm  to
       produce a result string.

       The  following  shell  script  compiles  /usr/src/cmd/cat.c and moves the output to a file
       named cat in the current directory when invoked with the argument /usr/src/cmd/cat or with
       the argument /usr/src/cmd/cat.c:

           c99 -- "$(dirname -- "$1")/$(basename -- "$1" .c).c" &&
           mv a.out "$(basename -- "$1" .c)"

       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.

RATIONALE

       The behaviors of basename and dirname 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 early proposal versions of these utilities due to the way it
       specified handling of trailing <slash> characters.

       Since the definition of pathname specifies implementation-defined behavior  for  pathnames
       starting  with  two  <slash>  characters,  this  volume  of POSIX.1‐2017 specifies similar
       implementation-defined behavior for the basename and dirname utilities.

FUTURE DIRECTIONS

       None.

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 .