1BASENAME(1P)               POSIX Programmer's Manual              BASENAME(1P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
10

NAME

12       basename — return non-directory portion of a pathname
13

SYNOPSIS

15       basename string [suffix]
16

DESCRIPTION

18       The string operand shall be treated as a pathname, as  defined  in  the
19       Base  Definitions volume of POSIX.1‐2017, Section 3.271, Pathname.  The
20       string string shall be converted to the filename corresponding  to  the
21       last pathname component in string and then the suffix string suffix, if
22       present, shall be removed. This shall be  done  by  performing  actions
23       equivalent to the following steps in order:
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25        1. If string is a null string, it is unspecified whether the resulting
26           string is '.'  or a null string.  In  either  case,  skip  steps  2
27           through 6.
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29        2. If  string is "//", it is implementation-defined whether steps 3 to
30           6 are skipped or processed.
31
32        3. If string consists entirely of <slash> characters, string shall  be
33           set to a single <slash> character. In this case, skip steps 4 to 6.
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35        4. If  there are any trailing <slash> characters in string, they shall
36           be removed.
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38        5. If there are any <slash> characters remaining in string, the prefix
39           of  string up to and including the last <slash> character in string
40           shall be removed.
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42        6. If the suffix operand is present, is not identical to  the  charac‐
43           ters remaining in string, and is identical to a suffix of the char‐
44           acters remaining in string, the suffix suffix shall be removed from
45           string.   Otherwise,  string is not modified by this step. It shall
46           not be considered an error if suffix is not found in string.
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48       The resulting string shall be written to standard output.
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OPTIONS

51       None.
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OPERANDS

54       The following operands shall be supported:
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56       string    A string.
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58       suffix    A string.
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STDIN

61       Not used.
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INPUT FILES

64       None.
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ENVIRONMENT VARIABLES

67       The following environment variables shall affect the execution of base‐
68       name:
69
70       LANG      Provide  a  default  value for the internationalization vari‐
71                 ables that are unset or null. (See the Base Definitions  vol‐
72                 ume  of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
73                 ables for the precedence  of  internationalization  variables
74                 used to determine the values of locale categories.)
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76       LC_ALL    If  set  to  a non-empty string value, override the values of
77                 all the other internationalization variables.
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79       LC_CTYPE  Determine the locale for the interpretation of  sequences  of
80                 bytes of text data as characters (for example, single-byte as
81                 opposed to multi-byte characters in arguments).
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83       LC_MESSAGES
84                 Determine the locale that should be used to affect the format
85                 and  contents  of  diagnostic  messages  written  to standard
86                 error.
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88       NLSPATH   Determine the location of message catalogs for the processing
89                 of LC_MESSAGES.
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ASYNCHRONOUS EVENTS

92       Default.
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STDOUT

95       The  basename  utility shall write a line to the standard output in the
96       following format:
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98
99           "%s\n", <resulting string>
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STDERR

102       The standard error shall be used only for diagnostic messages.
103

OUTPUT FILES

105       None.
106

EXTENDED DESCRIPTION

108       None.
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EXIT STATUS

111       The following exit values shall be returned:
112
113        0    Successful completion.
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115       >0    An error occurred.
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CONSEQUENCES OF ERRORS

118       Default.
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120       The following sections are informative.
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APPLICATION USAGE

123       The definition of pathname  specifies  implementation-defined  behavior
124       for pathnames starting with two <slash> characters. Therefore, applica‐
125       tions shall not arbitrarily add <slash> characters to the beginning  of
126       a  pathname unless they can ensure that there are more or less than two
127       or are prepared to deal with the implementation-defined consequences.
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EXAMPLES

130       If the string string is a valid pathname:
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132
133           $(basename -- "string")
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135       produces a filename that could be used to open the file named by string
136       in the directory returned by:
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139           $(dirname -- "string")
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141       If  the  string  string  is not a valid pathname, the same algorithm is
142       used, but the result need not be a valid filename. The basename utility
143       is  not expected to make any judgements about the validity of string as
144       a pathname; it just follows the specified algorithm to produce a result
145       string.
146
147       The  following  shell  script compiles /usr/src/cmd/cat.c and moves the
148       output to a file named cat in the current directory when  invoked  with
149       the argument /usr/src/cmd/cat or with the argument /usr/src/cmd/cat.c:
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151
152           c99 -- "$(dirname -- "$1")/$(basename -- "$1" .c).c" &&
153           mv a.out "$(basename -- "$1" .c)"
154
155       The  EXAMPLES section of the basename() function (see the System Inter‐
156       faces volume of POSIX.1‐2017,  basename())  includes  a  table  showing
157       examples  of  the results of processing several sample pathnames by the
158       basename() and dirname() functions and  by  the  basename  and  dirname
159       utilities.
160

RATIONALE

162       The  behaviors  of  basename  and dirname have been coordinated so that
163       when string is a valid pathname:
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165
166           $(basename -- "string")
167
168       would be a valid filename for the file in the directory:
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170
171           $(dirname -- "string")
172
173       This would not work for the early proposal versions of these  utilities
174       due to the way it specified handling of trailing <slash> characters.
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176       Since  the  definition  of  pathname  specifies  implementation-defined
177       behavior for pathnames starting with two <slash> characters, this  vol‐
178       ume  of  POSIX.1‐2017 specifies similar implementation-defined behavior
179       for the basename and dirname utilities.
180

FUTURE DIRECTIONS

182       None.
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SEE ALSO

185       Section 2.5, Parameters and Variables, dirname
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187       The Base Definitions volume of POSIX.1‐2017, Section  3.271,  Pathname,
188       Chapter 8, Environment Variables
189
190       The System Interfaces volume of POSIX.1‐2017, basename(), dirname()
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193       Portions  of  this text are reprinted and reproduced in electronic form
194       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
195       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
196       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
197       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
198       event of any discrepancy between this version and the original IEEE and
199       The  Open Group Standard, the original IEEE and The Open Group Standard
200       is the referee document. The original Standard can be  obtained  online
201       at http://www.opengroup.org/unix/online.html .
202
203       Any  typographical  or  formatting  errors that appear in this page are
204       most likely to have been introduced during the conversion of the source
205       files  to  man page format. To report such errors, see https://www.ker
206       nel.org/doc/man-pages/reporting_bugs.html .
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210IEEE/The Open Group                  2017                         BASENAME(1P)
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