huschi.net

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 (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 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.
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 com-
              pletely.

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 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  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).
       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 IEEE Std 1003.1-2001, 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 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 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
              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 val-
       ues for "normal error conditions" and the values above 128 can be  con-
       fused  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
       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 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,  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 Standard, 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)