Conditional variables

Shell Programming and Scripting
1

if {-a file}
if {-s file} what it will do

if {-z string} what it will do

please help on this

2

These are conditional expressions, which returns true or false on evaluating something for what they have defined. you would have square brackets instead of curly.

man test

for details.

      -a file
           True if file exists.
      -s file
           True if file exists and has a size greater than zero.
      -z s1
           True if the length of string s1 is zero.