On Sat, May 05, 2001 at 02:34:47PM -0700, Karsten M. Self wrote:
> This came up on another list. The problem involves testing existence of
> a Unix shell variable from another program with limited system
> interaction features.
...
> $?MYVAR
>
> ...which allows testing of presence of a variable.
>
> ...but I'm not aware of a similar bash/korn/bourne feature. Anyone?
Just as a side note: 'setenv MYVAR "/path:$MYVAR"' will fail in [t]csh
if MYVAR is not defined, hence constructs like
if ( $?MYVAR ) then
setenv MYVAR "/usr/local/myprog:$MYVAR"
else
setenv MYVAR "/usr/local/myprog"
endif
Bash will quite happily expand an undefined variable to a null string,
so the test above is not needed at all:
export MYVAR="/path:$MYVAR"
is all you need.
Dima
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