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       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

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.

       If the first argument is '−', the results are unspecified.

OPTIONS

       The  env  utility  shall  conform  to  the Base Definitions volume of POSIX.1‐2008, Section 12.2, Utility
       Syntax Guidelines, except for the unspecified usage of '−'.

       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 Section 2.14, 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 POSIX.1‐2008, Section 8.2, Internationalization  Variables  for  the
                 precedence   of   internationalization  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
                 POSIX.1‐2008, 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 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:

           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
       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  POSIX.1‐2008  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:"$PATH" $(getconf V7_ENV) mygrep xyz myfile

       invokes the command mygrep with a new PATH value as the only entry in  its  environment  other  than  any
       variables  required  by  the implementation for conformance. In this case, PATH is used to locate mygrep,
       which is expected to reside in /mybin.

RATIONALE

As with all other utilities that invoke other utilities, this volume of POSIX.1‐2008 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 removed − option in a manner compatible with
the Utility Syntax Guidelines. It is possible to create a non-conforming environment using the −i option,
as it may remove environment variables required by the implementation for conformance. The following will
preserve these environment variables as well as preserve the PATH for conforming utilities:

IFS='
'
# The preceding value should be <space><tab><newline>.
# Set IFS to its default value.

set −f
# disable pathname expansion

\unalias −a
# Unset all possible aliases.
# Note that unalias is escaped to prevent an alias
# being used for unalias.
# This step is not strictly necessary, since aliases are not inherited,
# and the ENV environment variable is only used by interactive shells,
# the only way any aliases can exist in a script is if it defines them
# itself.

unset −f env getconf
# Ensure env and getconf are not user functions.

env −i $(getconf V7_ENV) PATH="$(getconf PATH)" command

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.

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers,  Inc
       and  The  Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2013                                           ENV(1POSIX)