> Apart from your example above, even simple things like:
> if [ $f = 'y' ]
> will bomb out if $f is blank.
This is quite an important point for would be shell
scripters. The above reads to most programmers as
"if the contents of variable $f is equal to 'y'"
But in fact what happens is the shell substitutes in
the value of $f before calling the test command.
Hence if $f contains say "x" then the test command
sees
[ x = 'y' ]
and returns false, but if $f is blank then the shell
replacement of $f and the subsequent call of test sees
[ = 'y' ]
and hence the error. You need to put the $f in double
quotes so that the shell still sees $f and does the
substitution but if $f is blank test still gets a valid
condition,
[ "" = 'y' ]
HTH (or at least is moderately interesting)
P.
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