Defining bash function body using parenthesis instead of braces

Question

This script demonstrates defining a bash function with parenthesis verses with braces. The parenthesis have the nice effect of making environment variables created in the f

Answer 1

Both are valid, and as Carl mentioned any compound command can also be used, e.g.:

$ f() if [ "$1" = 'a' ]; then echo 'equals a'; fi
$ f a
equals a
$ f b
$

POSIX 7 2.9.5 Function Definition Command http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_09_05:

The format of a function definition command is as follows:

fname() compound-command[io-redirect ...]

[...] The argument compound-command represents a compound command, as described in Compound Commands.

Then 2.9.4 Compound Commands http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_09_04:

(compound-list) [...] Variable assignments and built-in commands that affect the environment shall not remain in effect after the list finishes.

{ compound-list;} Execute compound-list in the current process environment.

The semantics are the same as using () without a function definition: it does not create a new process, but gets executed in what POSIX and Bash call a "subshell environment".