strlen.sh

#!/bin/sh

string="abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"
loops=10000000

echo 'empty loop'
i=0
start=$(date +%s)
while [ $i -lt $loops ]; do
    :
    i=$((i+1))
done
echo "took $(($(date +%s) - start))s"

echo 'checking with = ""'
i=0
start=$(date +%s)
while [ $i -lt $loops ]; do
    [ "$string" = "" ]
    i=$((i+1))
done
echo "took $(($(date +%s) - start))s"

echo 'checking with = ${#} -ne 0'
i=0
start=$(date +%s)
while [ $i -lt $loops ]; do
    [ ${#string} -eq 0 ]
    i=$((i+1))
done
echo "took $(($(date +%s) - start))s"