====== Sample AWK questions ======

  * How to run awk command specified in a file?
''awk -f filename''

  * Write a command to print the squares of numbers from 1 to 10 using awk command
''awk 'BEGIN { for(i=1;i<=10;i++) {print "square of",i,"is",i*i;}}'''

  * Write a command to find the sum of bytes (size of file) of all files in a directory.
''ls -l | awk 'BEGIN {sum=0} {sum = sum + $5} END {print sum}'''

  * In the text file, some lines are delimited by colon and some are delimited by space. Write a command to print the third field of each line.

''awk '{ if( $0 ~ /:/ ) { FS=":"; } else { FS =" "; } print $3 }' filename''

  * Write a command to print the line number before each line?
''awk '{print NR, $0}' filename''

  * Write a command to print the second and third line of a file without using NR.
''awk 'BEGIN {RS="";FS="\n"} {print $2,$3}' filename''

  * Write a command to print zero byte size files?
''ls -l | awk '/^-/ {if ($5==0 ) print $9 }'''

  * Write a command to rename the files in a directory with "_new" as postfix?
''ls -F | awk '{print "mv "$1" "$1".new"}' | sh''

  * Write a command to find the total number of lines in a file without using NR
''awk 'BEGIN {sum=0} {sum=sum+1} END {print sum}' filename''

Another way to print the number of lines is by using the NR. The command is

''awk 'END{print NR}' filename''