--- name: "basename" section: "1p" platform: "linux" package: "man-pages" version: "6.19-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/basename/1p" --- # basename(1p) return non-directory portion of a pathname ## 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 \ characters, *string* shall be set to a single \ character. In this case, skip steps 4 to 6. - 4\. If there are any trailing \ characters in *string*, they shall be removed. - 5\. If there are any \ characters remaining in *string*, the prefix of *string* up to and including the last \ 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", ``` ## 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 \ characters. Therefore, applications shall not arbitrarily add \ 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 \ characters. Since the definition of *pathname* specifies implementation-defined behavior for pathnames starting with two \ 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* 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()*, *dirname()* ## 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 .