# basename

## 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.
    


* * *