1ENV(1P) POSIX Programmer's Manual ENV(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 env - set the environment for command invocation
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15 env [-i][name=value]... [utility [argument...]]
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18 The env utility shall obtain the current environment, modify it accord‐
19 ing to its arguments, then invoke the utility named by the utility op‐
20 erand with the modified environment.
21 Optional arguments shall be passed to utility.
23 If no utility operand is specified, the resulting environment shall be
25 written to the standard output, with one name= value pair per line.
26
28 The env utility shall conform to the Base Definitions volume of
29 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
30 The following options shall be supported:
32 -i Invoke utility with exactly the environment specified by the
34 arguments; the inherited environment shall be ignored com‐
35 pletely.
36
39 The following operands shall be supported:
40 name=value
42 Arguments of the form name= value shall modify the execution
43 environment, and shall be placed into the inherited environment
44 before the utility is invoked.
45 utility
47 The name of the utility to be invoked. If the utility operand
48 names any of the special built-in utilities in Special Built-In
49 Utilities, the results are undefined.
50 argument
52 A string to pass as an argument for the invoked utility.
53
56 Not used.
57
59 None.
60
62 The following environment variables shall affect the execution of env:
63 LANG Provide a default value for the internationalization variables
65 that are unset or null. (See the Base Definitions volume of
66 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
67 ables for the precedence of internationalization variables used
68 to determine the values of locale categories.)
69 LC_ALL If set to a non-empty string value, override the values of all
71 the other internationalization variables.
72 LC_CTYPE
74 Determine the locale for the interpretation of sequences of
75 bytes of text data as characters (for example, single-byte as
76 opposed to multi-byte characters in arguments).
77 LC_MESSAGES
79 Determine the locale that should be used to affect the format
80 and contents of diagnostic messages written to standard error.
81 NLSPATH
83 Determine the location of message catalogs for the processing of
84 LC_MESSAGES .
85 PATH Determine the location of the utility, as described in the Base
87 Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environ‐
88 ment Variables. If PATH is specified as a name= value operand to
89 env, the value given shall be used in the search for utility.
90
93 Default.
94
96 If no utility operand is specified, each name= value pair in the
97 resulting environment shall be written in the form:
98 "%s=%s\n", <name>, <value>
101 If the utility operand is specified, the env utility shall not write to
103 standard output.
104
106 The standard error shall be used only for diagnostic messages.
107
109 None.
110
112 None.
113
115 If utility is invoked, the exit status of env shall be the exit status
116 of utility; otherwise, the env utility shall exit with one of the fol‐
117 lowing values:
118 0 The env utility completed successfully.
120 1-125 An error occurred in the env utility.
122 126 The utility specified by utility was found but could not be
124 invoked.
125 127 The utility specified by utility could not be found.
127
130 Default.
131 The following sections are informative.
133
135 The command, env, nice, nohup, time, and xargs utilities have been
136 specified to use exit code 127 if an error occurs so that applications
137 can distinguish "failure to find a utility" from "invoked utility
138 exited with an error indication". The value 127 was chosen because it
139 is not commonly used for other meanings; most utilities use small val‐
140 ues for "normal error conditions" and the values above 128 can be con‐
141 fused with termination due to receipt of a signal. The value 126 was
142 chosen in a similar manner to indicate that the utility could be found,
143 but not invoked. Some scripts produce meaningful error messages differ‐
144 entiating the 126 and 127 cases. The distinction between exit codes 126
145 and 127 is based on KornShell practice that uses 127 when all attempts
146 to exec the utility fail with [ENOENT], and uses 126 when any attempt
147 to exec the utility fails for any other reason.
148 Historical implementations of the env utility use the execvp() or exe‐
150 clp() functions defined in the System Interfaces volume of
151 IEEE Std 1003.1-2001 to invoke the specified utility; this provides
152 better performance and keeps users from having to escape characters
153 with special meaning to the shell. Therefore, shell functions, special
154 built-ins, and built-ins that are only provided by the shell are not
155 found.
156
158 The following command:
159 env -i PATH=/mybin mygrep xyz myfile
162 invokes the command mygrep with a new PATH value as the only entry in
164 its environment. In this case, PATH is used to locate mygrep, which
165 then must reside in /mybin.
166
168 As with all other utilities that invoke other utilities, this volume of
169 IEEE Std 1003.1-2001 only specifies what env does with standard input,
170 standard output, standard error, input files, and output files. If a
171 utility is executed, it is not constrained by the specification of
172 input and output by env.
173 The -i option was added to allow the functionality of the withdrawn -
175 option in a manner compatible with the Utility Syntax Guidelines.
176 Some have suggested that env is redundant since the same effect is
178 achieved by:
179 name=value ... utility [ argument ... ]
182 The example is equivalent to env when an environment variable is being
184 added to the environment of the command, but not when the environment
185 is being set to the given value. The env utility also writes out the
186 current environment if invoked without arguments. There is sufficient
187 functionality beyond what the example provides to justify inclusion of
188 env.
189
191 None.
192
194 Parameters and Variables, Special Built-In Utilities
195
197 Portions of this text are reprinted and reproduced in electronic form
198 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
199 -- Portable Operating System Interface (POSIX), The Open Group Base
200 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
201 Electrical and Electronics Engineers, Inc and The Open Group. In the
202 event of any discrepancy between this version and the original IEEE and
203 The Open Group Standard, the original IEEE and The Open Group Standard
204 is the referee document. The original Standard can be obtained online
205 at http://www.opengroup.org/unix/online.html .
206IEEE/The Open Group 2003 ENV(1P)