> Note that it's not even a bug here; it's necessary for disambiguation. I would call it a bug when there's one valid way to read it, and [ fails to see it. I

> Note that it's not even a bug here; it's necessary for disambiguation. I would call it a bug when there's one valid way to read it, and [ fails to see it. I don't see the ambiguation. For example, zsh's [ doesn't have these errors: $ a=1; b=1; c='!'; d='!' $ [ "$a" = "$b" -a "$c" = "$d" ]; echo $? 0 $ [ '!' '(' "$c" = "$d" ')' ]; echo $? 1 Same result with FreeBSD's tcsh's [. I think bash's [ is just lacking the ability to backtrack while parsing its arguments. Curiously, GNU's [ fails to parse the arguments of the first, but not the second's: $ command [ "$a" = "$b" -a "$c" = "$d" ]; echo $? [: extra argument ‘!’ 2 $ command [ '!' '(' "$c" = "$d" ')' ]; echo $? 1 It seems its argument parsing works differently when using parentheses: $ command [ "$a" = "$b" -a '(' "$c" = "$d" ')' ]; echo $? 0