AWK Examples

As a second example, suppose you have several thousand files you want to move into a new directory and rename by appending a .dat to the filenames. You could do this one by one (several hours), or use vi to make a decent command file to do it (several minutes), or use awk (several seconds).

Suppose the files are named junk* (* is wildcard for any sequence of characters), and need to be moved to ../iraf and have a '.dat' appended to the name. To do this type

ls junk* | awk '{print "mv "$0" ../iraf/"$0".dat"}' | csh

Print first two fields in opposite order:

  awk '{ print $2, $1 }' file

Print lines longer than 45 characters

  awk 'length > 45' file

Print length of string in 4th column

  awk '{print length($4)}' file

Add up first column, print sum and average

       
{ s += $1 }
END  { print "sum is", s, " average is", s/NR }

Print fields in reverse order

awk '{ for (i = NF; i > 0; --i) print $i }' file

Print the last line

      {line = $0}
           END {print line}

Print the total number of lines that contain the word Mike

  /Mike/ {nlines = nlines + 1}
  END {print nlines}

Print all lines between start/stop pairs

  awk '/start/, /stop/' file

Print all lines whose first field is different from previous one

  awk '$1 != prev { print; prev = $1 }' file

Print column 3 if column 1 > column 2

  awk '$1 > $2 {print $3}' file

Print line if column 3 > column 2

  awk '$3 > $2' file

Count number of lines where col 3 > col 1

  
awk '$3 > $1 {print i + "1"; i++}' file

Print sequence number and then column 1 of file

  awk '{print NR, $1}' file

Print every line after erasing the 2nd field

  awk '{$2 = ""; print}' file

Print hi 28 times

  yes | head -28 | awk '{ print "hi" }'

Print hi.0010 to hi.0099

  
yes | head -90 | awk '{printf("hi00%2.0f n", NR+9)}'

Print out 4 random numbers between 0 and 1

yes | head -4 | awk '{print rand()}'

Print out 40 random integers modulo 5

yes | head -40 | awk '{print int(100*rand()) % 5}'

Replace every field by its absolute value

  
{ for (i = 1; i <= NF; i=i+1) if ($i < 0) $i = -$i print}

If you have another character that delimits fields, use the -F option

For example, to print out the phone number for Jones in the following file
# 000902|Smith|Theodore|333-242-2222|149092
# 000901|Jones|Bill|532-382-0342|234023
# ...
# type

  awk -F"|" '$2=="Jones"{print $4}' filename

Some looping commands
Remove a bunch of print jobs from the queue

  
BEGIN{
	for (i=175;i>133;i--){
	printf "lprm -Plw %dn", i
	} exit
     }