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ENV(P) ENV(P)
NAME
env - set the environment for command invocation
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:
-i Invoke utility with exactly the environment specified by the arguments; the
inherited environment shall be ignored completely.
OPERANDS
The following operands shall be supported:
name=value
Arguments of the form name= value shall modify the execution environment,
and shall be placed into the inherited environment before the utility is
invoked.
utility
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.
argument
A string to pass as an argument for the invoked utility.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of env:
LANG 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 interna-
tionalization variables used to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all the other
internationalization variables.
LC_CTYPE
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).
LC_MESSAGES
Determine the locale that should be used to affect the format and contents
of diagnostic messages written to standard error.
NLSPATH
Determine the location of message catalogs for the processing of LC_MESSAGES
.
PATH 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.
ASYNCHRONOUS EVENTS
Default.
STDOUT
If no utility operand is specified, each name= value pair in the resulting environ-
ment 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:
0 The env utility completed successfully.
1-125 An error occurred in the env utility.
126 The utility specified by utility was found but could not be invoked.
127 The utility specified by utility could not be found.
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 con-
fused 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() func-
tions 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 environ-
ment. 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 .
POSIX 2003 ENV(P)
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