(..)
around test command to avoid subshell
overhead.([ "$x" -gt 0 ]) && foo
[ "$x" -gt 0 ] && foo
You are wrapping a single test command in (..)
, creating
an unnecessary subshell. This serves no purpose, but is significantly
slower:
$ 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, and can be ignored for stylistic reasons.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.