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

       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.

       env — set the environment for command invocation

       env [−i] [name=value]... [utility [argument...]]

       The env utility shall obtain the current environment, modify it accord‐
       ing  to its arguments, then invoke the utility named by the utility op‐
       erand 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.

       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  com‐

       The following operands shall be supported:

		 Arguments  of	the form name=value shall modify the execution
		 environment, and shall be placed into the inherited  environ‐
		 ment 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.

       Not used.


       The following environment variables shall affect the execution of env:

       LANG	 Provide  a  default  value for the internationalization vari‐
		 ables that are unset or null. (See the Base Definitions  vol‐
		 ume  of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
		 ables 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).

		 Determine the locale that should be used to affect the format
		 and  contents	of  diagnostic	messages  written  to standard

       NLSPATH	 Determine the location of message catalogs for the processing

       PATH	 Determine  the	 location  of the utility, as described in the
		 Base Definitions volume of POSIX.1‐2008, Chapter 8,  Environ‐
		 ment Variables.  If PATH is specified as a name=value operand
		 to env, the value given shall be used in the search for util‐


       If no utility operand is specified, each name=value pair in the result‐
       ing 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.

       The standard error shall be used only for diagnostic messages.



       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  fol‐
       lowing 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

	 127   The utility specified by utility could not be found.


       The following sections are informative.

       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  val‐
       ues  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 differ‐
       entiating 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  exe‐
       clp() 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.

       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.

       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 out‐
       put 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:

	   # 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


       Section	2.14,  Special Built-In Utilities, Section 2.5, Parameters and

       The Base Definitions volume of  POSIX.1‐2008,  Chapter  8,  Environment
       Variables, Section 12.2, Utility Syntax Guidelines

       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 Electri‐
       cal  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.ker‐
       nel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group		     2013			       ENV(1P)

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