Function guardLine

shell/plugins/menu/MenuModel.js:457–460

(id, tag, expression)

}

function guardLine(id, tag, expression) {
  return "if { " + substituteGuardReaders(expression) + "; } >/dev/null 2>&1; then echo "
    + id + ":" + tag + ":1; else echo " + id + ":" + tag + ":0; fi\n"
}

// One bash script for every `when:` and `checked:` in the menu, reporting
// `<id>:<w|c>:<0|1>` per line. Speed is the whole point: the menu opens on