Linux man pages

Section (1) env

Linux manual pages	Section 1

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 _zsingle_quotesz_PIPE_zsingle_quotesz_, or a signal number like _zsingle_quotesz_13_zsingle_quotesz_. 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 _zsingle_quotesz_−S_zsingle_quotesz_ parameter the script will likely fail with:

/usr/bin/env: _zsingle_quotesz_perl −w −T_zsingle_quotesz_: 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 _zsingle_quotesz_env −−default-signal=PIPE seq inf | head −n1_zsingle_quotesz_

NOTES

POSIX_zsingle_quotesz_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/>

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