What is the difference between these two Bash if-statements? e.g.
if [ "$FOO" = "true" ]; then
vs
if [ $FOO = "true" ]; then
What is the difference? It seems that both statements work the same.
If the value of $FOO is a single word that doesn't contain a wildcard character \[*?, then the two are identical.
If $FOO is unassigned, or empty, or more than one word (i.e., contains whitespace or $IFS), then the unquoted version is a syntax error. If it happens to be just the right sequence of words (such as 0 -eq 0 -o false), the result could be arbitrary. Therefore, it is good practice to always quote variables in shell scripts.
Incidentally, "true" does not need to be quoted.
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