1. Inserting a new line after every 2 lines
We will see how to implement this using the awk command with an example.
The input "file.txt" contains the below data:
1 A
2 B
3 C
4 D
5 E
6 F
Let say, we want to insert the new line "9 Z" after every two lines in the input file. The required output data after inserting a new line looks as
1 A
2 B
9 Z
3 C
4 D
9 Z
5 E
6 F
9 Z
The awk command for getting this output is
awk '{
if(NR%2 == 0)
{
print $0"\n9 Z";
}
else
{
print $0
}
}' file.txt
2. Replace the Nth occurrence of a pattern
The input file contains the data.
AAA 1
BBB 2
CCC 3
AAA 4
AAA 5
BBB 6
CCC 7
AAA 8
BBB 9
AAA 0
Now we want to replace the fourth occurrence of the first filed "AAA" with "ZZZ" in the file.
The required output is:
AAA 1
BBB 2
CCC 3
AAA 4
AAA 5
BBB 6
CCC 7
ZZZ 8
BBB 9
AAA 0
The awk command for getting this output is
awk 'BEGIN {count=0}
{
if($1 == "AAA")
{
count++
}
if(count == 4)
{
sub("AAA","ZZZ",$1)
}
}
{
print $0
}' file.txt
3. Find the sum of even and odd lines separately
The input file data:
A 10
B 39
C 22
D 44
E 75
F 89
G 67
You have to get the second field and then find the sum the even and odd lines.
The required output is
174, 172
The awk command for producing this output is
awk '{
if(NR%2 == 1)
{
sum_e = sum_e + $2
}
else
{
sum_o = sum_o + $2
}
}
END { print sum_e,sum_o }' file.txt
4. Fibonacci series using awk command
Now we will produce the Fibonacci series using the awk command.
awk ' BEGIN{
for(i=0;i<=10;i++)
{
if (i <=1 )
{
x=0;
y=1;
print i;
}
else
{
z=x+y;
print z;
x=y;
y=z;
}
}
}'
The output is
0
1
1
2
3
5
8
13
21
34
55
5. Remove leading zeros from a file using the awk command. The input file contains the below data.
0012345
05678
01010
00001
After removing the leading zeros, the output should contain the below data.
12345
5678
1010
1
The awk command for this is.
awk '{print $1 + 0}' file.txt
awk '{printf "%d\n",$0}' file.txt
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