ENV(1P)                                             POSIX Programmer's Manual                                            ENV(1P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult 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.

OPTIONS
       The env utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guide-
       lines.

       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  Spe-
              cial 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  international-
              ization 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 stan-
              dard 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, Chap-
              ter 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 Korn-
       Shell 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 Syn-
       tax 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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                       ENV(1P)