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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 dif-
       fer (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.

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  utili-
              ties 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  prece-
              dence 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  exam-
              ple, 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 writ-
              ten 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 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 dis-
       tinction 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 envi-
       ronment 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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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                  2003                              ENV(1P)