Awk

awk

pattern {action}
pattern {action}

$ awk '{print $2}' /etc/fstab

$ awk '/^[^#]/ {print $2}' /etc/fstab

to filter out comment lines - starting with #

print first field from password file using field seperator ':'

$ awk -F: '{print$1}' /etc/passwd

print only user ID > 500

$ awk -F: '$3>=500 {print$1}' /etc/passwd

display average of numbers entereed on a line:

$ awk '{ sum=0; for (i=1; i<=NF; i++) sum +=$i; print sum/NF; }'

NF