awk

pattern {action}
pattern {action}

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

to filter out comment lines - starting with #

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

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	number of fields in the current line
NR	the current record number (line number)
FS	input field seperator (space by default)
RS	record seperator (newline by default)
Example	Example
Example	Example
Example	Example
Example	Example
Example	Example

Awk