env
env runs a command with a changed environment — the set of NAME=VALUE variables a process inherits. Run with no command, it prints the current environment instead.
env [options] [NAME=VALUE]... [command [arg]...]
$ env LANG=C TZ=UTC my-program
$ env
PATH=/bin
HOME=/home/jack
...
How it works #
You give env a list of NAME=VALUE assignments, then a command. env applies the assignments to its own environment and then runs the command, which inherits the result. The assignments affect only that one run — your shell's environment is untouched.
This is the clean way to run something with a particular variable set, without changing it for everything else, and the standard way to run a command with one variable temporarily different.
With no command, env simply prints the environment it would have used — which, with no options, is the current one.
Building the environment #
| Option | Effect |
|---|---|
-i, --ignore-environment | Start from an empty environment, not the inherited one — so the command sees only what you assign. A bare - argument means the same. |
-u, --unset=NAME | Remove NAME from the environment. |
--file=FILE | Read NAME=VALUE lines from a .env-style FILE and apply them. |
The order is: start (inherited, or empty with -i), apply --file, apply --unset, apply the NAME=VALUE arguments.
Running the command #
| Option | Effect |
|---|---|
-C, --chdir=DIR | Change to DIR before running the command. |
--argv0=NAME | Run the command but present NAME as its zeroth argument. |
-S, --split-string=S | Split S into separate arguments. This exists for script interpreter lines, where everything after the interpreter arrives as one string. |
Signal handling #
env can adjust how the command treats signals before launching it:
| Option | Effect |
|---|---|
--ignore-signal[=SIG] | Set the named signals to be ignored. |
--default-signal[=SIG] | Reset the named signals to their default handling. |
--block-signal[=SIG] | Block delivery of the named signals while the command runs. |
--list-signal-handling | List the signal-handling changes the other options requested. |
Other options #
| Option | Effect |
|---|---|
-0, --null | When printing the environment, end each line with a NUL character instead of a newline. Not valid together with a command. |
-v, --debug | Print each processing step env performs. |
Exit status #
When env runs a command, it exits with that command's status. The exception is a failure in env itself:
| Code | Meaning |
|---|---|
| (command's own) | The command ran; this is its exit status. |
125 | env itself failed — for example, a bad option. |
126 | The command was found but could not be run. |
127 | The command was not found. |