(..)
is a subshell. Did you mean [ .. ]
, a test expression?if ( 1 -lt 2 )
then
echo "1 is less than 2"
fi
if [ 1 -lt 2 ]
then
echo "1 is less than 2"
fi
Tests like -eq
to check numeric equality or
\<
for string comparison only work are actually
parameters to the test
command, and only work as tests in
that context. [
is an alias for test
, so
you'll frequently see them written as [ 1 -eq 2 ]
.
( .. )
is completely unrelated, and is a subshell mostly
used to scope shell modifications. They should not be used in
if
or while
statements in shell scripts.
If you wanted to test a condition, rewrite the ( .. )
to
[ .. ]
.
This error is triggered by having a binary operator as the first
parameter in a subshell, and could falsely trigger on e.g.
if ( grep -eq "foo|bar" file )
. In these cases, check
whether the subshell is actually needed.
Note that there's a similar looking error SC2204 with a low false positive rate.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.