Manual Page - env(1p)
Manual Reference Pages - ENV (P)
NAME
env - set the environment for command invocation
CONTENTS
Synopsis
Description
Options
Operands
Stdin
Input Files
Environment Variables
Asynchronous Events
Stdout
Stderr
Output Files
Extended Description
Exit Status
Consequences Of Errors
Application Usage
Examples
Rationale
Future Directions
See Also
Copyright
SYNOPSIS
env [-i][name=value]...
[utility
[argument...]]
DESCRIPTION
The env utility shall obtain the current environment, modify
it according to its arguments, then invoke the utility named
by the utility operand with the modified environment.
Optional arguments shall be passed to utility.
If no utility operand is specified, the resulting environment
shall be written to the standard output, with one
name= value pair per line.
OPTIONS
The env utility shall conform to the Base Definitions volume
of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
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-i
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Invoke utility with exactly the environment specified by the
arguments; the inherited environment shall be ignored
completely.
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OPERANDS
The following operands shall be supported:
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name=value
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Arguments of the form name= value shall modify the execution
environment, and shall be placed into the inherited
environment before the utility is invoked.
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utility
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The name of the utility to be invoked. If the utility operand
names any of the special built-in utilities in Special Built-In
Utilities , the results are undefined.
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argument
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A string to pass as an argument for the invoked utility.
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STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of
env:
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LANG
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Provide a default value for the internationalization variables that
are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables
for
the precedence of internationalization variables used to determine
the values of locale categories.)
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LC_ALL
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If set to a non-empty string value, override the values of all the
other internationalization variables.
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LC_CTYPE
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Determine the locale for the interpretation of sequences of bytes
of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments).
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LC_MESSAGES
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Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard
error.
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NLSPATH
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Determine the location of message catalogs for the processing of LC_MESSAGES
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PATH
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Determine the location of the utility, as described in the Base
Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environment
Variables. If PATH is specified as a name= value
operand to env, the value given shall be used in the search
for utility.
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ASYNCHRONOUS EVENTS
Default.
STDOUT
If no utility operand is specified, each name= value
pair in the resulting environment shall be written in
the form:
"%s=%s\n", <name>, <value>
If the utility operand is specified, the env utility shall
not write to standard output.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
If utility is invoked, the exit status of env shall be
the exit status of utility; otherwise, the
env utility shall exit with one of the following values:
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0
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The env utility completed successfully.
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1-125
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An error occurred in the env utility.
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126
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The utility specified by utility was found but could not be
invoked.
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127
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The utility specified by utility could not be found.
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CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
The command, env, nice, nohup, time,
and xargs utilities have been specified to use exit code 127
if an error occurs so that
applications can distinguish "failure to find a utility" from "invoked
utility exited with an error indication". The value 127
was chosen because it is not commonly used for other meanings; most
utilities use small values for "normal error conditions" and
the values above 128 can be confused with termination due to receipt
of a signal. The value 126 was chosen in a similar manner to
indicate that the utility could be found, but not invoked. Some scripts
produce meaningful error messages differentiating the 126
and 127 cases. The distinction between exit codes 126 and 127 is based
on KornShell practice that uses 127 when all attempts to
exec the utility fail with [ENOENT], and uses 126 when any attempt
to exec the utility fails for any other
reason.
Historical implementations of the env utility use the execvp()
or execlp() functions defined in the System Interfaces volume
of IEEE Std 1003.1-2001
to invoke the specified utility; this provides better performance
and keeps users from having to escape characters with special
meaning to the shell. Therefore, shell functions, special built-ins,
and built-ins that are only provided by the shell are not
found.
EXAMPLES
The following command:
env -i PATH=/mybin mygrep xyz myfile
invokes the command mygrep with a new PATH value as the
only entry in its environment. In this case, PATH
is used to locate mygrep, which then must reside in /mybin.
RATIONALE
As with all other utilities that invoke other utilities, this volume
of IEEE Std 1003.1-2001 only specifies what
env does with standard input, standard output, standard error,
input files, and output files. If a utility is executed, it
is not constrained by the specification of input and output by env.
The -i option was added to allow the functionality of the withdrawn
- option in a manner compatible with the
Utility Syntax Guidelines.
Some have suggested that env is redundant since the same effect
is achieved by:
name=value ... utility [ argument ... ]
The example is equivalent to env when an environment variable
is being added to the environment of the command, but not
when the environment is being set to the given value. The env
utility also writes out the current environment if invoked
without arguments. There is sufficient functionality beyond what the
example provides to justify inclusion of env.
FUTURE DIRECTIONS
None.
SEE ALSO
Parameters and Variables , Special
Built-In Utilities
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
| IEEE/The Open Group | ENV (P) | 2003 |
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