basename(1p) — Linux manual page

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

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

       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(3p)) 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.

SEE ALSO

       Section 2.5, Parameters and Variables, dirname(1p)

       The Base Definitions volume of POSIX.1‐2017, Section 3.271,
       Pathname, Chapter 8, Environment Variables

       The System Interfaces volume of POSIX.1‐2017, basename(3p),
       dirname(3p)

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 .

IEEE/The Open Group               2017                      BASENAME(1P)

Pages that refer to this page: dirname(1p), basename(3p), dirname(3p)

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