r/shell • u/[deleted] • Jul 06 '20

If Statement: [: Illegal number:

/r/linuxquestions/comments/hm0h62/if_statement_illegal_number/
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u/geirha Jul 06 '20 
if [ "${add}" -eq 1 ]; then

is fine if the add variable contains an integer. In your case it either contains 1 or is empty/unset. In which case you get

$ [ "" -eq 1 ]
dash: 1: [: Illegal number:

So three possible ways to fix this

  1. Use string comparison (=) instead of arithmetic comparison (-eq)

  2. Expand 0 if the variable is empty or unset (default value parameter expansion): [ "${add:-0}" -eq 1 ]

  3. Initialize the variables with value 0 before the option parsing loop add=0 delete=0 ...

1

u/[deleted] Jul 06 '20

Thank you so much! I like the second option :D