Это может работать для вас:
echo '1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26' |
sed 's/^\(\([^,]*,\)\{21\}\([^,]*,\)\([^,]*,\)\{2\}\)[^,]*,/\1\3/'
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,22,26
или, если вы предпочитаете:
echo '1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26' |
sed -r 's/^(([^,]*,){21}([^,]*,)([^,]*,){2})[^,]*,/\1\3/'
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,22,26