# dirname

## 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



           dirname — return the directory portion of a pathname
    


## SYNOPSIS



           dirname _string_
    


## 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 name of the
           directory containing the filename corresponding to the last
           pathname component in _string_ , performing actions equivalent to the
           following steps in order:
    
            1. If _string_ is **//** , skip steps 2 to 5.
    
            2. If _string_ consists entirely of <slash> characters, _string_
               shall be set to a single <slash> character. In this case, skip
               steps 3 to 8.
    
            3. If there are any trailing <slash> characters in _string_ , they
               shall be removed.
    
            4. If there are no <slash> characters remaining in _string_ , _string_
               shall be set to a single <period> character. In this case,
               skip steps 5 to 8.
    
            5. If there are any trailing non-<slash> characters in _string_ ,
               they shall be removed.
    
            6. If the remaining _string_ is **//** , it is implementation-defined
               whether steps 7 and 8 are skipped or processed.
    
            7. If there are any trailing <slash> characters in _string_ , they
               shall be removed.
    
            8. If the remaining _string_ is empty, _string_ shall be set to a
               single <slash> character.
    
           The resulting string shall be written to standard output.
    


## OPTIONS



           None.
    


## OPERANDS



           The following operand shall be supported:
    
           _string_    A string.
    


## STDIN



           Not used.
    


## INPUT FILES



           None.
    


## ENVIRONMENT VARIABLES



           The following environment variables shall affect the execution of
           _dirname_ :
    
           _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 _dirname_ 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



           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.
    
           See also the examples for the _basename_ utility.
    


## RATIONALE



           The behaviors of _basename_ and _dirname_ in this volume of
           POSIX.1‐2017 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 early
           proposals due to the way processing of trailing <slash> characters
           was specified. Consideration was given to leaving processing
           unspecified if there were trailing <slash> characters, but this
           cannot be done; the Base Definitions volume of POSIX.1‐2017,
           _Section 3.271_ , _Pathname_ allows trailing <slash> characters. The
           _basename_ and _dirname_ utilities have to specify consistent handling
           for all valid pathnames.
    


## FUTURE DIRECTIONS



           None.
    


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