ENV

Section: User Commands (1)
Updated: April 2020
Page Index
 

NAME

env - run a program in a modified environment  

SYNOPSIS

env [,OPTION/]... [,-/] [,NAME=VALUE/]... [,COMMAND /[,ARG/]...]  

DESCRIPTION

Set each NAME to VALUE in the environment and run COMMAND.

Mandatory arguments to long options are mandatory for short options too.

-i, --ignore-environment
start with an empty environment
-0, --null
end each output line with NUL, not newline
-u, --unset=,NAME/
remove variable from the environment
-C, --chdir=,DIR/
change working directory to DIR
-S, --split-string=,S/
process and split S into separate arguments; used to pass multiple arguments on shebang lines
--block-signal[=,SIG/]
block delivery of SIG signal(s) to COMMAND
--default-signal[=,SIG/]
reset handling of SIG signal(s) to the default
--ignore-signal[=,SIG/]
set handling of SIG signals(s) to do nothing
--list-signal-handling
list non default signal handling to stderr
-v, --debug
print verbose information for each processing step
--help
display this help and exit
--version
output version information and exit

A mere - implies -i. If no COMMAND, print the resulting environment.

SIG may be a signal name like 'PIPE', or a signal number like '13'. Without SIG, all known signals are included. Multiple signals can be comma-separated.  

OPTIONS

 

-S/--split-string usage in scripts

The -S option allows specifying multiple parameters in a script. Running a script named 1.pl containing the following first line:

#!/usr/bin/env -S perl -w -T
...

Will execute perl -w -T 1.pl.

Without the '-S' parameter the script will likely fail with:

/usr/bin/env: 'perl -w -T': No such file or directory

See the full documentation for more details.

 

--default-signal[=SIG] usage

This option allows setting a signal handler to its default action, which is not possible using the traditional shell trap command. The following example ensures that seq will be terminated by SIGPIPE no matter how this signal is being handled in the process invoking the command.

sh -c 'env --default-signal=PIPE seq inf | head -n1'

 

NOTES

POSIX's exec(2) pages says:
"many existing applications wrongly assume that they start with certain signals set to the default action and/or unblocked.... Therefore, it is best not to block or ignore signals across execs without explicit reason to do so, and especially not to block signals across execs of arbitrary (not closely cooperating) programs."
 

AUTHOR

Written by Richard Mlynarik, David MacKenzie, and Assaf Gordon.  

REPORTING BUGS

GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>  

COPYRIGHT

Copyright © 2020 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.  

SEE ALSO

sigaction(2), sigprocmask(2), signal(7)


Full documentation <https://www.gnu.org/software/coreutils/env>
or available locally via: info '(coreutils) env invocation'


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
-S/--split-string usage in scripts
--default-signal[=SIG] usage
NOTES
AUTHOR
REPORTING BUGS
COPYRIGHT
SEE ALSO
LinuxReviews : manual page archive : man1