1DIRNAME(P) POSIX Programmer's Manual DIRNAME(P)
2
6 dirname - return the directory portion of a pathname
7
9 dirname string
10
12 The string operand shall be treated as a pathname, as defined in the
13 Base Definitions volume of IEEE Std 1003.1-2001, Section 3.266, Path‐
14 name. The string string shall be converted to the name of the directory
15 containing the filename corresponding to the last pathname component in
16 string, performing actions equivalent to the following steps in order:
17 1. If string is //, skip steps 2 to 5.
19 2. If string consists entirely of slash characters, string shall be
21 set to a single slash character. In this case, skip steps 3 to 8.
22 3. If there are any trailing slash characters in string, they shall be
24 removed.
25 4. If there are no slash characters remaining in string, string shall
27 be set to a single period character. In this case, skip steps 5 to
28 8.
29 5. If there are any trailing non-slash characters in string, they
31 shall be removed.
32 6. If the remaining string is //, it is implementation-defined whether
34 steps 7 and 8 are skipped or processed.
35 7. If there are any trailing slash characters in string, they shall be
37 removed.
38 8. If the remaining string is empty, string shall be set to a single
40 slash character.
41 The resulting string shall be written to standard output.
43
45 None.
46
48 The following operand shall be supported:
49 string A string.
51
54 Not used.
55
57 None.
58
60 The following environment variables shall affect the execution of
61 dirname:
62 LANG Provide a default value for the internationalization variables
64 that are unset or null. (See the Base Definitions volume of
65 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
66 ables for the precedence of internationalization variables used
67 to determine the values of locale categories.)
68 LC_ALL If set to a non-empty string value, override the values of all
70 the other internationalization variables.
71 LC_CTYPE
73 Determine the locale for the interpretation of sequences of
74 bytes of text data as characters (for example, single-byte as
75 opposed to multi-byte characters in arguments).
76 LC_MESSAGES
78 Determine the locale that should be used to affect the format
79 and contents of diagnostic messages written to standard error.
80 NLSPATH
82 Determine the location of message catalogs for the processing of
83 LC_MESSAGES .
84
87 Default.
88
90 The dirname utility shall write a line to the standard output in the
91 following format:
92 "%s\n", <resulting string>
95
97 The standard error shall be used only for diagnostic messages.
98
100 None.
101
103 None.
104
106 The following exit values shall be returned:
107 0 Successful completion.
109 >0 An error occurred.
111
114 Default.
115 The following sections are informative.
117
119 The definition of pathname specifies implementation-defined behavior
120 for pathnames starting with two slash characters. Therefore, applica‐
121 tions shall not arbitrarily add slashes to the beginning of a pathname
122 unless they can ensure that there are more or less than two or are pre‐
123 pared to deal with the implementation-defined consequences.
124
126 Command Results
127 dirname / /
128 dirname // / or //
129 dirname /a/b/ /a
130 dirname //a//b// //a
131 dirname Unspecified
132 dirname a . ($? = 0)
134 dirname "" . ($? = 0)
135 dirname /a /
136 dirname /a/b /a
137 dirname a/b a
138
140 The dirname utility originated in System III. It has evolved through
141 the System V releases to a version that matches the requirements speci‐
142 fied in this description in System V Release 3. 4.3 BSD and earlier
143 versions did not include dirname.
144 The behaviors of basename and dirname in this volume of
146 IEEE Std 1003.1-2001 have been coordinated so that when string is a
147 valid pathname:
148 $(basename "string")
151 would be a valid filename for the file in the directory:
153 $(dirname "string")
156 This would not work for the versions of these utilities in early pro‐
158 posals due to the way processing of trailing slashes was specified.
159 Consideration was given to leaving processing unspecified if there were
160 trailing slashes, but this cannot be done; the Base Definitions volume
161 of IEEE Std 1003.1-2001, Section 3.266, Pathname allows trailing
162 slashes. The basename and dirname utilities have to specify consistent
163 handling for all valid pathnames.
164
166 None.
167
169 basename() , Parameters and Variables
170
172 Portions of this text are reprinted and reproduced in electronic form
173 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
174 -- Portable Operating System Interface (POSIX), The Open Group Base
175 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
176 Electrical and Electronics Engineers, Inc and The Open Group. In the
177 event of any discrepancy between this version and the original IEEE and
178 The Open Group Standard, the original IEEE and The Open Group Standard
179 is the referee document. The original Standard can be obtained online
180 at http://www.opengroup.org/unix/online.html .
181IEEE/The Open Group 2003 DIRNAME(P)