A Handful of Useful awk One-Liners

A Handful of Useful awk One-Liners

Although awk can be used to write programs of some complexity,
many useful programs are not complicated. Here is a collection
of short programs that you might find handy and/or
instructive:

1.Print the total numnber of input lines:

END { print NR }

2.Print the tenth input line:

NR == 10

3.Print the last field of every input line:

{ print $NF }

4.Print the last field of the last input line:

{ field = $NF}
END { print field }

5.Print every input line with more than 4 fields:

NF > 4

6.Print every input line in which the last field is more than 4:

$NF > 4

7.Print the total number of fields in all input lines:

{ nf = nf + NF }
END { print nf }

8.Print the total number of lines that contain Beth:

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

9.Print the largest first fields and the line that contains it
( assumes some $1 is positive):

$1 > max { max = $1 ; maxlines = $0 }
END { print max, maxline)


10.Print every line that has at least one field:

NF > 0

11.Pritn every line longer than 80 characters:

length($0) > 80

12.Print the numer of fields in every line, followed by the line itself:

{ print NF, $0 }

13.Print the first two fields, in opposite order, of every line:

{ print $2, $1 }

14.Exchange the first two fields of every line and then print the line:

{ temp = $1 ; $1 = $2 ; $2 = temp ; print }

15.Print every line witg rge first field replaced by the line number:

{ $1 = NR ; print }

16.Print every line after erasing the second field:

{ $2 = ""; print }

17.Print in reverse order the fields of every line:

{ for (i=NF ; i>0 ; i=i-1) printf( "%s ", $1)
printf("\n")
}

18.Print the sums of the fields of every line:

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

19.Ad up all fields in all lines and print the sum:

{ for ( i=1 ; i<=NF ; i=i+1 ) sum = sum + $i}
END { print sum }


20.Print every line after replacing each field by its absolute value:

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

Source: The AWK Programming Language