env — run a program in a modified environment
Examples (TL;DR)
-
Show the environment:
env -
Run a program. Often used in scripts after the shebang (#!) for looking up the path to the program:
env program -
Clear the environment and run a program:
env -i program -
Remove variable from the environment and run a program:
env -u variable program -
Set a variable and run a program:
env variable=value program
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."
Reporting Bugs
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>
Copyright
Copyright © 2019 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'
Referenced By
environ(7), guestfs-release-notes(1), guestfs-release-notes-1.32(1), ksh93(1), mosh(1), pkgconf(1), pmpython(1), procenv(1), tgif.1x(1).