how can i output the number 2641569270623 from a text file called checkpoint.txt that is a one line file (generated by a maths sieving program) that looks like:
pmin=2641569270623,factor_count=8,cpu_secs=1705.793,frac_done=0.002592,elapsed_secs=1710.844

i tried sed -n "/pmin=/,/,factor/ p" checkpoint.txt | sed "$ d" which ouputs nothing and sed -n "/pmin=/,/,factor/ p" checkpoint.txt which output the whole line