bash : syntax to compute modulus

Question

What is correct bash syntax for modulus ?

My script has a loop that needs to take some action each 100 repetitions ( such as write to a log ) :

counter = 0
...
divisor = 100
remainder = 0
remainder = counter%=divisor
if $remainder = 0; then ...; else ... ; fi

but I receive error :

counter%=divisor: command not found

You seem to be having more basic problems. You can't have spaces around = in variable assignments. — Barmar
– Barmar, Commented Mar 12, 2015 at 1:13
Your script does not look at all like Bash -- or if it is, it's very bizarre Bash. counter = 0, for example, calls the program counter with the arguments = and 0. — ruakh
– ruakh, Commented Mar 12, 2015 at 1:13
does bash include the concept of declaring and initializing a variable ? — BaltoStar
– BaltoStar, Commented Mar 12, 2015 at 4:47
obLink to shellcheck.net here. Check your script for basic syntax errors before posting, please. — tripleee
– tripleee, Commented Mar 12, 2015 at 8:17

kojiro · Accepted Answer · 2015-03-12 01:12:23Z

3

There are a few different ways to get arithmetic context in bash. I usually use double parens

(( remainder = counter % divisor ))

answered Mar 12, 2015 at 1:12

kojiro

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2 Comments

if (( counter % divisor )) -eq 0; then ... yields " syntax error near unexpected token '-eq' "

The proper syntax for that is if (( counter % divisor == 0 )); then