A simple bash function that imitates the functionality of log rotate

rotate.sh

#!/usr/bin/env bash

# Immitates log rotate.
# You should change maxsize and rotatemax to your own use case.
rotate() {
    local file=$1
    local rotatemax=9      # The max number of numbered files to keep around
    local maxsize=2097152  # After the main file passes this threshold rotate occurs
    local filesize=$(wc -c $file | cut -f 1 -d ' ')

    if [[ $filesize -gt $maxsize ]]; then
        if [[ -s ${file}.1 ]]; then
            gzip ${file}.1
        fi
        for i in $(eval echo {$rotatemax..1}); do
            if [[ -s ${file}.${i}.gz ]]; then
                mv ${file}.${i}.gz ${file}.$(( i + 1 )).gz
            fi
        done
    fi
}