If there is no assignment of environment variable following `env`, what kind of environment is a command executed with?

Question

env runs a command with a modified environment.

env [option]... [name=value]... [command [args]...]

If there is no name=value or option following env, what kind of environment is a command executed with?

What is the purpose of using env without any name=value or option following?

env bash -c 'echo "$_"'

Thanks.

Do you mean see bash: set: No such file or directory after running env bash -f 'set'? — Tim, Commented Aug 2, 2017 at 16:03
set display all the shell variables and functions. What is it to do with environment variables? — Tim, Commented Aug 2, 2017 at 16:26

Ulrich Schwarz · Accepted Answer · 2017-08-02 16:08:02Z

1

The output of

env cat /proc/self/environ

suggests that the environment is unchanged if nothing else is given.

(Or indeed, if I had bothered to read the fine manual, 'If no COMMAND, print the resulting environment', so plain env will be just fine.)

answered Aug 2, 2017 at 16:05

Ulrich Schwarz

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Thanks. Then what is the difference between using env and not using env? What is the purpose of using env without any assignment following?
– Tim
Commented Aug 2, 2017 at 16:06
"no COMMAND" is indeed a totally different situation from no name=value and option
– Tim
Commented Aug 2, 2017 at 16:09
1

@Tim: you might find unix.stackexchange.com/a/29620/3929 helpful. In a nutshell, it can make sure you call a binary, not an alias or function, without knowing where exactly it is (other than in $PATH).
– Ulrich Schwarz
Commented Aug 2, 2017 at 16:11

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