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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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BASENAME(1P) POSIX Programmer's Manual BASENAME(1P)
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.
basename — return non-directory portion of a pathname
basename string [suffix]
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.
None.
The following operands shall be supported:
string A string.
suffix A string.
Not used.
None.
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.
Default.
The basename utility shall write a line to the standard output in
the following format:
"%s\n", <resulting string>
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
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.
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.
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.
None.
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)
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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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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