Portable Shell Boundaries

Portable Test

Single-Bracket Conditions

[ is widely available in POSIX-style shells. Simple numeric and string checks can stay portable when a script does not need Bash-only syntax.

Program

Play the script to choose a status value and see the portable test branch.

portable_test.sh 
#!/usr/bin/env bash

status=
if [ "$status" -eq 0 ]; then
    result="ok"
else
    result="fail"
fi
echo "status:$result"

#!/usr/bin/env bash

status=
if [ "$status" -eq 0 ]; then
    result="ok"
else
    result="fail"
fi
echo "status:$result"
portable test `[` works in POSIX-style shells for simple comparisons.
numeric comparison `-eq` compares integer values.
boundary Use Bash-only `[[ ... ]]` when you need its extra features; otherwise `[` can keep a script easier to port.