shell-guide

Personal shell script guide.

Control statements

Prefer `good_condition || return 1` to `bad_condition && return 1`

What you want:

You may want to replace a simple if block with a one-liner.

func_intended() {
    # ...
    if [ -z "$SOME_VAR" ]; then
        printf "ERROR\n"
        return 1
    fi
    return # info: $? is 0
}

Problematic code:

func_problematic() {
    # ...
    [ -z "$SOME_VAR" ] && { printf "ERROR\n"; return 1; }
    return # warning: $? is 1
}

Correct code:

func_correct() {
    # ...
    [ -n "$SOME_VAR" ] || { printf "ERROR\n"; return 1; }
    return # info: $? is 0
}

Note:

It seems the current version of ShellCheck fails to find this kind of programming errors at the time of writing. It detects an issue in code like A && B || C but it is a different type of problem. See ShellScheck SC2015 regarding A && B || C.

Code snippets

See wiki for code snippets.

References

ShellCheck is a great tool.