Bash argument escaping

bash-escape.js

// Implement bash string escaping.
var safePattern =    /^[a-z0-9_\/\-.,?:@#%^+=\[\]]*$/i;
var safeishPattern = /^[a-z0-9_\/\-.,?:@#%^+=\[\]{}|&()<>; *']*$/i;
function bashEscape(arg) {
  // These don't need quoting
  if (safePattern.test(arg)) return arg;

  // These are fine wrapped in double quotes using weak escaping.
  if (safeishPattern.test(arg)) return '"' + arg + '"';

  // Otherwise use strong escaping with single quotes
  return "'" + arg.replace(/'+/g, function (val) {
    // But we need to interpolate single quotes efficiently

    // One or two can simply be '\'' -> ' or '\'\'' -> ''
    if (val.length < 3) return "'" + val.replace(/'/g, "\\'") + "'";

    // But more in a row, it's better to wrap in double quotes '"'''''"' -> '''''
    return "'\"" + val + "\"'";

  }) + "'";
}

@kriskowal Right on... I thought I knew sh/bash OK, but I'm finding surprises in playing with this. Bash is wacky... which begs the question, why are we still using it? It really should be deprecated in favor of A) a very simple interactive shell and B) a real language for serious scripting (Nodejs is great :-)

@creationix Speaking of context, you should add a usage example... I think I know what you're up to, and it's dead simple, but...