BASENAME(1) General Commands Manual BASENAME(1)

basename — return nondirectory portion of pathname

basename string [suffix]

The string operand shall be treated as a pathname, as defined in 2.2.2.102. 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 //, it is implementation defined whether steps (2) through (5) are skipped or processed.
  2. If string consists entirely of slash characters, string shall be set to a single slash character. In this case, skip steps (3) through (5).
  3. If there are any trailing slash characters in string, they shall be removed.
  4. 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.
  5. 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

shall not be 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.

None.

The following operands shall be supported by the implementation:

string

A string.

suffix

A string.

None.

None.

The following environment variables shall affect the execution of basename:

This variable shall determine the locale to use for the locale categories when both LC_ALL and the corresponding environment variable (beginning with LC_ ) do not specify a locale. See 2.6.

This variable shall determine the locale to be used to override any values for locale categories specified by the settings of LANG or any environment variables beginning with LC_.

This variable shall determine the locale for the interpretation of sequences of bytes of text data as characters (e.g., single- versus multibyte characters in arguments).

This variable shall determine the language in which messages should be written.

Default.

The basename utility shall write a line to the standard output in the following format: "%s\n", <resulting string>

Used only for diagnostic messages.

None.

None.

The basename utility shall exit with one of the following values:

Successful completion.

An error occurred.

Default.

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: c89 $(dirname "$1")/$( basename "$1" .c).c mv a.out $( basename "$1" .c)

The . 1 {8} definition of pathname allows trailing slashes on a pathname naming a directory. Some historical implementations have not allowed trailing slashes and thus treated pathnames of this form in other ways. Existing implementations also differ in their handling of suffix when suffix matches the entire string left after removing the directory part of string. The behaviors of basename and dirname in this standard 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 earlier drafts due to the way it specified handling of trailing slashes. Since the definition of pathname in 2.2.2.102 specifies implementation-defined behavior for pathnames starting with two slash characters, Draft 11 has been changed to specify similar implementation-defined behavior for the basename and dirname utilities. On implementations where the pathname // is always treated the same as the pathname /, the functionality required by Draft 10 meets all of the Draft 11 requirements.

September 1991 posix.fail