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Are the following two boolean expressions the same?
if [ -n $1 ] ; then
if [ -n "$1" ] ; then
And these two
if [ $? == 0 ] ; then
if [ "$?" == 0 ] ; then
If not – When should you put a variable in quotes?
put variables in quotes when there is any chance that the value may contain white spaces, or in general NOT be a continuous string of characters. So
as
$?should always be something between 0 and 255, you don’t need to quote that because it is a return value set after each sub-process returns. It is NOT possible to break that by assigning a string value directly, i.e.because a user variable name must start with [A-Za-z_] , so don’t do that 😉
Whereas for $1, if a value is passed in like
the test
will blow up,
but the test
will succeed.
IHTH