3 ms·

That may be true in older shells, but in modern shells [ $x == "" ] is valid, and "" is a single token whose value is the empty string. But I've seen old code t

by _kst_ 10y ago

That may be true in older shells, but in modern shells [ $x == "" ] is valid, and "" is a single token whose value is the empty string. But I've seen old code that does things like if [ x$x == "x" ] ; then ... apparently because it was necessary at one time.

kqr 10y ago
It depends on what you mean by "older" shells. More modern shells tend to support this properly, but the baseline for most shell scripts is /bin/sh which is not guaranteed to be modern – it is often a new release of Sh.