1HASH(1P) POSIX Programmer's Manual HASH(1P)
2
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
13 hash — remember or report utility locations
14
16 hash [utility...]
17 hash −r
19
21 The hash utility shall affect the way the current shell environment
22 remembers the locations of utilities found as described in Section
23 2.9.1.1, Command Search and Execution. Depending on the arguments
24 specified, it shall add utility locations to its list of remembered
25 locations or it shall purge the contents of the list. When no arguments
26 are specified, it shall report on the contents of the list.
27 Utilities provided as built-ins to the shell shall not be reported by
29 hash.
30
32 The hash utility shall conform to the Base Definitions volume of
33 POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.
34 The following option shall be supported:
36 −r Forget all previously remembered utility locations.
38
40 The following operand shall be supported:
41 utility The name of a utility to be searched for and added to the
43 list of remembered locations. If utility contains one or more
44 <slash> characters, the results are unspecified.
45
47 Not used.
48
50 None.
51
53 The following environment variables shall affect the execution of hash:
54 LANG Provide a default value for the internationalization vari‐
56 ables that are unset or null. (See the Base Definitions vol‐
57 ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
58 ables for the precedence of internationalization variables
59 used to determine the values of locale categories.)
60 LC_ALL If set to a non-empty string value, override the values of
62 all the other internationalization variables.
63 LC_CTYPE Determine the locale for the interpretation of sequences of
65 bytes of text data as characters (for example, single-byte as
66 opposed to multi-byte characters in arguments).
67 LC_MESSAGES
69 Determine the locale that should be used to affect the format
70 and contents of diagnostic messages written to standard
71 error.
72 NLSPATH Determine the location of message catalogs for the processing
74 of LC_MESSAGES.
75 PATH Determine the location of utility, as described in the Base
77 Definitions volume of POSIX.1‐2008, Chapter 8, Environment
78 Variables.
79
81 Default.
82
84 The standard output of hash shall be used when no arguments are speci‐
85 fied. Its format is unspecified, but includes the pathname of each
86 utility in the list of remembered locations for the current shell envi‐
87 ronment. This list shall consist of those utilities named in previous
88 hash invocations that have been invoked, and may contain those invoked
89 and found through the normal command search process.
90
92 The standard error shall be used only for diagnostic messages.
93
95 None.
96
98 None.
99
101 The following exit values shall be returned:
102 0 Successful completion.
104 >0 An error occurred.
106
108 Default.
109 The following sections are informative.
111
113 Since hash affects the current shell execution environment, it is
114 always provided as a shell regular built-in. If it is called in a sepa‐
115 rate utility execution environment, such as one of the following:
116 nohup hash −r
118 find . −type f | xargs hash
119 it does not affect the command search process of the caller's environ‐
121 ment.
122 The hash utility may be implemented as an alias—for example, alias
124 −t −, in which case utilities found through normal command search are
125 not listed by the hash command.
126 The effects of hash −r can also be achieved portably by resetting the
128 value of PATH; in the simplest form, this can be:
129 PATH="$PATH"
131 The use of hash with utility names is unnecessary for most applica‐
133 tions, but may provide a performance improvement on a few implementa‐
134 tions; normally, the hashing process is included by default.
135
137 None.
138
140 None.
141
143 None.
144
146 Section 2.9.1.1, Command Search and Execution
147 The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
149 Variables, Section 12.2, Utility Syntax Guidelines
150
152 Portions of this text are reprinted and reproduced in electronic form
153 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
154 -- Portable Operating System Interface (POSIX), The Open Group Base
155 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
156 cal and Electronics Engineers, Inc and The Open Group. (This is
157 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
158 event of any discrepancy between this version and the original IEEE and
159 The Open Group Standard, the original IEEE and The Open Group Standard
160 is the referee document. The original Standard can be obtained online
161 at http://www.unix.org/online.html .
162 Any typographical or formatting errors that appear in this page are
164 most likely to have been introduced during the conversion of the source
165 files to man page format. To report such errors, see https://www.ker‐
166 nel.org/doc/man-pages/reporting_bugs.html .
167IEEE/The Open Group 2013 HASH(1P)