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I need braces to specify evaluation priority of expressions, but I don't want braces to create sub-scripts. Look what happens when that example code is ran:

Example script

#!/bin/bash

false || (echo "First" && exit 1)
false || (echo "Second" && exit 2)
exit 3

Output

First
Second

It seems that braces create sub-scripts, where exit doesn't cause the main script to exit.

What is the most elegant way to do what I want? Preferably without blocks and nesting. Thanks!

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2
  • Is removing the parentheses not enough for you? I know it's not proper arithmetic logic, but it will evaluate across in order, and should achieve what I think it is supposed to.
    – Wally
    Commented Jan 16, 2014 at 18:58
  • @Wally - yes, in that specific example it would fit, but I really would like to know, how to prioritize expressions (in general) without creating sub-shells.
    – java.is.for.desktop
    Commented Jan 16, 2014 at 19:03

1 Answer 1

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12

These () are parentheses, and they launch a subshell

These {} are braces, and they are for grouping within the current shell. exit will exit your script.

Note the whitespace requirements are more stringent ({ needs to be followed by whitespace; } needs to be preceded by a semicolon plus whitespace, or a newline)

false || { echo foo; echo bar; }     # this is OK
false || {echo foo; echo bar}        # not OK

See Grouping Commands in the manual for the details.

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  • 1
    } needs to be preceded by a command separator, regardless of whether it's a newline, semicolon, or ampersand.
    – Ignacio Vazquez-Abrams
    Commented Jan 16, 2014 at 19:51
  • Thank you, it works! I even skimmed over the topic of "grouping in BASH" some time ago, but didn't associated it with evaluation priority.
    – java.is.for.desktop
    Commented Jan 20, 2014 at 15:37

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