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Use $((..)) instead of deprecated $[..].

Problematic code

n=1
n=$[n+1]

Correct code

n=1
n=$((n+1))

Rationale

The $[..] syntax was deprecated in Bash 2.0 and replaced with the standard $((..)) syntax from Korn shell

Exceptions

None.

See also

• http://unix.stackexchange.com/questions/209833/what-does-a-dollar-sign-followed-by-a-square-bracket-mean-in-bash

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