bash - Test if user passed in a shell variable -

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i have shell function check if user passed in second variable. have tried not seem working

function dash() {     if [ -z "$2" ];         open dash://$1:$2;     else         open dash://$1;     fi }

basically, want if second argument $2 passed in 'x' else 'y'

just do:

function dash() {   open dash://$1${2+:}$2 }

the ${2+:} expands : if $2 set, , null string otherwise.


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