Ubuntu Manpage: basename - return non-directory portion of a pathname

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
IEEE Std 1003.1-2001, Section 3.266, 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 IEEE Std 1003.1-2001, 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 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

       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)

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 slashes.

       Since the definition of pathname specifies implementation-defined behavior for  pathnames  starting  with
       two  slash  characters,  this  volume  of  IEEE Std 1003.1-2001  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, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (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.opengroup.org/unix/online.html .