(..)around condition to avoid subshell overhead.
if ([ "$x" -gt 0 ]) then true; fi
if [ "$x" -gt 0 ] then true; fi
The shell syntax is
while cmd and
until cmd without any parentheses. Instead, parentheses are an independent construct used to create subshells.
ShellCheck has noticed that you're wrapping
(..) around one or more test commands. This is unnecessary, and the resulting fork adds quite a lot of overhead:
$ i=0; time while ( [ "$i" -lt 10000 ] ); do i=$((i+1)); done real 0m6.998s user 0m3.453s sys 0m3.464s $ i=0; time while [ "$i" -lt 10000 ]; do i=$((i+1)); done real 0m0.055s user 0m0.054s sys 0m0.001s
Just delete the surrounding
(..) since they serve no purpose and only slows the script down.
This issue only affects performance, not correctness, so it can be safely ignored.
If you are considering doing it to stylistically match C-like languages, please note that this is not conventional and that you'd probably recommend someone use
if (1 == 2) over
if (system("[ 1 = 2 ]")) in C no matter which language they're used to.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.