Though it is an obsoleted part of the XSI standard, many implementations still support multiple expressions with Boolean operators and parenthesis.

The (obsolete) operators are listed below with decreasing precedence.

( expression )
expression -a expression
expression -o expression

Using these (obsolete) operators, a complex shell expression:

if [ "$a" -gt 0 ] && { [ "$b" -ne 2 ] || [ "$b" -e 0 ]; }
then ...
fi

Could be written with one invocation of test(1):

if [ "$a" -gt 0 -a '(' "$b" -ne 2 -o "$c" -ne 0 ')' ]
then ...
fi