Output a running count of lines

README.md

linecounter2 is an alternate version that goes to the previous line, erases it and rewrites with new info. Might be useful if you need the newline character at the end of the string (for example to flush an output buffer).

linecounter

#!/usr/bin/env bash

# Output a running counter of lines passed to the script.
# Optionally, if you know the total count you can give it as an argument.
#
# Example (bash):
# for i in $(seq 50000); do echo "line content"; done | linecounter 50000
#
# To preserve the original output, use tee:
# for i in $(seq 50000); do echo "line content"; done | tee output.log | linecounter 50000

line_nr=0

while read -r line; do
    line_nr=$((line_nr + 1))
    printf "\r%'d" $line_nr
    test -n "$1" && printf "/%'d" $1
done

echo

linecounter2

#!/usr/bin/env bash

# Output a running counter of lines passed to the script.
# Optionally, if you know the total count you can give it as an argument.
#
# Example (bash):
# for i in $(seq 50000); do echo "line content"; done | linecounter 50000
#
# To preserve the original output, use tee:
# for i in $(seq 50000); do echo "line content"; done | tee output.log | linecounter 50000

line_nr=0

echo
while read -r line; do
    line_nr=$((line_nr + 1))
    tput cuu1                        # move cursor up 1 line
    tput el                          # erase line
    printf "%'d" $line_nr            # output number formatted according to locale
    test -n "$1" && printf "/%'d" $1 # output total amount if given
    echo
done

Demo:

linecounter_demo.mp4