Revisions to bash if not multiple conditions without subshell?

Remove inaccurate data, expand example showing how to test the fact of a subshell. This is the only answer that gives a *demonstration* of this rather than only referring to the docs, so it's well worth keeping.

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edited Sep 10, 2016 at 2:11

Wildcard

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I want to use them just for grouping, but is it actually spawning a subshell? (How can I tell?)

It's not spawning a subshell. TheYes, the commands within the (...) just groups the commands and runs themare run in the existing shella subshell.

EDIT: ToTo test whether you're in a subshell you can compare the PID of your current shell with the PID of the interactive shell.

echo $BASHPID; (echo $BASHPID);

It turns out I was wrong. The commands within the (...) are run inExample output, demonstrating that parentheses spawn a subshell. and curly braces do not:

$ echo $BASHPID; (echo $BASHPID); { echo $BASHPID;}
50827
50843
50827
$

It's not spawning a subshell. The (...) just groups the commands and runs them in the existing shell.

EDIT: To test whether you're in a subshell you can compare the PID of your current shell with the PID of the interactive shell.

echo $BASHPID; (echo $BASHPID);

It turns out I was wrong. The commands within the (...) are run in a subshell.

I want to use them just for grouping, but is it actually spawning a subshell? (How can I tell?)

Yes, the commands within the (...) are run in a subshell.

To test whether you're in a subshell you can compare the PID of your current shell with the PID of the interactive shell.

echo $BASHPID; (echo $BASHPID);

Example output, demonstrating that parentheses spawn a subshell and curly braces do not:

$ echo $BASHPID; (echo $BASHPID); { echo $BASHPID;}
50827
50843
50827
$

added 257 characters in body

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edited Dec 4, 2015 at 15:32

David King

3.2k
12
25

It's not spawning a subshell. The (...) just groups the commands and runs them in the existing shell.

EDIT: To test whether you're in a subshell you can compare the PID of your current shell with the PID of the interactive shell.

echo $BASHPID; (echo $BASHPID);

It turns out I was wrong. The commands within the (...) are run in a subshell.

It's not spawning a subshell. The (...) just groups the commands and runs them in the existing shell.

EDIT: To test whether you're in a subshell you can compare the PID of your current shell with the PID of the interactive shell.

echo $BASHPID; (echo $BASHPID);

It turns out I was wrong. The commands within the (...) are run in a subshell.

Source Link

answered Dec 3, 2015 at 18:34

David King

3.2k
12
25

It's not spawning a subshell. The (...) just groups the commands and runs them in the existing shell.

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