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
