Bash, Re-writing a Line

There are instances when writing a shell script that you want to write to the same line over and over. This is mainly used for progress meters that update the same screen position over and over. Most languages represent a carriage return without newline as the \r escape sequence. In shell, it's no different, but there is one small caveat. The echo command requires two arguments.

#!/bin/bash

# simplest progress meter
items=100000
for ((i=0; i<$items; i+=1)); do
    echo -n -e "Processed $i/$items\r"
done

The -n argument to echo tells it to suppress the implicit newline that it usually includes. The -e argument tells it to respect escape sequences such as \r.