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
12 hash — remember or report utility locations
13
15 hash [utility...]
16 hash -r
18
20 The hash utility shall affect the way the current shell environment
21 remembers the locations of utilities found as described in Section
22 2.9.1.1, Command Search and Execution. Depending on the arguments
23 specified, it shall add utility locations to its list of remembered
24 locations or it shall purge the contents of the list. When no arguments
25 are specified, it shall report on the contents of the list.
26 Utilities provided as built-ins to the shell shall not be reported by
28 hash.
29
31 The hash utility shall conform to the Base Definitions volume of
32 POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
33 The following option shall be supported:
35 -r Forget all previously remembered utility locations.
37
39 The following operand shall be supported:
40 utility The name of a utility to be searched for and added to the
42 list of remembered locations. If utility contains one or more
43 <slash> characters, the results are unspecified.
44
46 Not used.
47
49 None.
50
52 The following environment variables shall affect the execution of hash:
53 LANG Provide a default value for the internationalization vari‐
55 ables that are unset or null. (See the Base Definitions vol‐
56 ume of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
57 ables for the precedence of internationalization variables
58 used to determine the values of locale categories.)
59 LC_ALL If set to a non-empty string value, override the values of
61 all the other internationalization variables.
62 LC_CTYPE Determine the locale for the interpretation of sequences of
64 bytes of text data as characters (for example, single-byte as
65 opposed to multi-byte characters in arguments).
66 LC_MESSAGES
68 Determine the locale that should be used to affect the format
69 and contents of diagnostic messages written to standard
70 error.
71 NLSPATH Determine the location of message catalogs for the processing
73 of LC_MESSAGES.
74 PATH Determine the location of utility, as described in the Base
76 Definitions volume of POSIX.1‐2017, Chapter 8, Environment
77 Variables.
78
80 Default.
81
83 The standard output of hash shall be used when no arguments are speci‐
84 fied. Its format is unspecified, but includes the pathname of each
85 utility in the list of remembered locations for the current shell envi‐
86 ronment. This list shall consist of those utilities named in previous
87 hash invocations that have been invoked, and may contain those invoked
88 and found through the normal command search process.
89
91 The standard error shall be used only for diagnostic messages.
92
94 None.
95
97 None.
98
100 The following exit values shall be returned:
101 0 Successful completion.
103 >0 An error occurred.
105
107 Default.
108 The following sections are informative.
110
112 Since hash affects the current shell execution environment, it is
113 always provided as a shell regular built-in. If it is called in a sepa‐
114 rate utility execution environment, such as one of the following:
115 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"
132 The use of hash with utility names is unnecessary for most applica‐
134 tions, but may provide a performance improvement on a few implementa‐
135 tions; normally, the hashing process is included by default.
136
138 None.
139
141 None.
142
144 None.
145
147 Section 2.9.1.1, Command Search and Execution
148 The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment
150 Variables, Section 12.2, Utility Syntax Guidelines
151
153 Portions of this text are reprinted and reproduced in electronic form
154 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
155 table Operating System Interface (POSIX), The Open Group Base Specifi‐
156 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
157 Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/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 2017 HASH(1P)