hash(1p)

1HASH(1P)                   POSIX Programmer's Manual                  HASH(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.
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NAME

12       hash - remember or report utility locations
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SYNOPSIS

15       hash [utility...]
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17       hash -r
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DESCRIPTION

21       The hash utility shall affect the way  the  current  shell  environment
22       remembers  the  locations  of  utilities  found as described in Command
23       Search and Execution . Depending on the arguments specified,  it  shall
24       add  utility  locations to its list of remembered locations or it shall
25       purge the contents of the list. When no  arguments  are  specified,  it
26       shall report on the contents of the list.
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28       Utilities  provided  as built-ins to the shell shall not be reported by
29       hash.
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OPTIONS

32       The hash utility shall  conform  to  the  Base  Definitions  volume  of
33       IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
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35       The following option shall be supported:
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37       -r     Forget all previously remembered utility locations.
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OPERANDS

41       The following operand shall be supported:
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43       utility
44              The  name  of a utility to be searched for and added to the list
45              of  remembered  locations.  If  utility  contains  one  or  more
46              slashes, the results are unspecified.
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STDIN

50       Not used.
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INPUT FILES

53       None.
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ENVIRONMENT VARIABLES

56       The following environment variables shall affect the execution of hash:
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58       LANG   Provide  a  default value for the internationalization variables
59              that are unset or null. (See  the  Base  Definitions  volume  of
60              IEEE Std 1003.1-2001,  Section  8.2,  Internationalization Vari‐
61              ables for the precedence of internationalization variables  used
62              to determine the values of locale categories.)
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64       LC_ALL If  set  to a non-empty string value, override the values of all
65              the other internationalization variables.
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67       LC_CTYPE
68              Determine the locale for  the  interpretation  of  sequences  of
69              bytes  of  text  data as characters (for example, single-byte as
70              opposed to multi-byte characters in arguments).
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72       LC_MESSAGES
73              Determine the locale that should be used to  affect  the  format
74              and contents of diagnostic messages written to standard error.
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76       NLSPATH
77              Determine the location of message catalogs for the processing of
78              LC_MESSAGES .
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80       PATH   Determine the location of utility, as described in the Base Def‐
81              initions  volume of IEEE Std 1003.1-2001, Chapter 8, Environment
82              Variables.
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ASYNCHRONOUS EVENTS

86       Default.
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STDOUT

89       The standard output of hash shall be used when no arguments are  speci‐
90       fied.  Its  format  is  unspecified,  but includes the pathname of each
91       utility in the list of remembered locations for the current shell envi‐
92       ronment.  This  list shall consist of those utilities named in previous
93       hash invocations that have been invoked, and may contain those  invoked
94       and found through the normal command search process.
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STDERR

97       The standard error shall be used only for diagnostic messages.
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OUTPUT FILES

100       None.
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EXTENDED DESCRIPTION

103       None.
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EXIT STATUS

106       The following exit values shall be returned:
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108        0     Successful completion.
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110       >0     An error occurred.
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CONSEQUENCES OF ERRORS

114       Default.
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116       The following sections are informative.
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APPLICATION USAGE

119       Since  hash  affects  the  current  shell  execution environment, it is
120       always provided as a shell regular built-in. If it is called in a sepa‐
121       rate utility execution environment, such as one of the following:
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123
124              nohup hash -r
125              find . -type f | xargs hash
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127       it  does not affect the command search process of the caller's environ‐
128       ment.
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130       The hash utility may be implemented  as  an  alias-for  example,  alias
131       -t -,  in  which case utilities found through normal command search are
132       not listed by the hash command.
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134       The effects of hash -r can also be achieved portably by  resetting  the
135       value of PATH ; in the simplest form, this can be:
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138              PATH="$PATH"
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140       The  use  of  hash  with utility names is unnecessary for most applica‐
141       tions, but may provide a performance improvement on a  few  implementa‐
142       tions; normally, the hashing process is included by default.
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EXAMPLES

145       None.
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RATIONALE

148       None.
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FUTURE DIRECTIONS

151       None.
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COPYRIGHT

157       Portions  of  this text are reprinted and reproduced in electronic form
158       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
159       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
160       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
161       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
162       event of any discrepancy between this version and the original IEEE and
163       The  Open Group Standard, the original IEEE and The Open Group Standard
164       is the referee document. The original Standard can be  obtained  online
165       at http://www.opengroup.org/unix/online.html .
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169IEEE/The Open Group                  2003                             HASH(1P)