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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 .