Declaring variables from data, and running multiple commands on data in one line of code

Question

I've come across an error today and would like other people's opinions on a solution beyond what I have. The error is in a dataset. The data in the last column/field of the first and second row/record should be the same, and the second to last column/field of row/record 1 is always "1". The problem is when this is not so and and the steps needed to correct it.

The incorrect data is as such, in a file called "sample.txt":

5@Comedia   @5@3@2@3@1/2  @3@1.6  @1@2 1/2@11@14 1/4
3@Melanistic@3@4@2@4@1 1/2@4@2 3/4@3@5    @2 @4 3/4
2@Pure      @4@5@5@5@3 1/2@5@4 3/4@5@8    @3 @6 1/2
4@Profit    @2@2@1@2@1.6  @1@1.6  @2@2 1/2@4 @6 1/2
1@Whammy    @1@1@1@1@1.6  @2@1.6  @4@5 1/2@5 @8 1/4

The correct data should look like this:

 5@Comedia   @5@3@2@3@1/2  @3@1.6  @1@2 1/2 @1@4 3/4
 3@Melanistic@3@4@2@4@1 1/2@4@2 3/4@3@5     @2@4 3/4
 2@Pure      @4@5@5@5@3 1/2@5@4 3/4@5@8     @3@6 1/2
 4@Profit    @2@2@1@2@1.6  @1@1.6  @2@2 1/2 @4@6 1/2
 1@Whammy    @1@1@1@1@1.6  @2@1.6  @4@5 1/2 @5@8 1/4

My current solution is a multi-step process I have a feeling can be streamlined. Any suggestions are highly appreciated.

1)Create a bash variable:

 length=$(cat sample.txt |awk -F@ 'NR==2{print $NF}') 

2)Create a file with the correct information in row 1:

awk -F@ -v l="$length" 'NR==1{$(NF-1)=1;$NF=l;print $0}' OFS=@ sample.txt >sample1.txt

3)Append the remaining info to the created correct row file

awk -F@ 'NR>1{print $0}' sample.txt >>sample1.txt   

Is there an awk, sed, or Perl one liner (or combinations of pipes) that can accomplish the three steps above in one?

Answer 1

If I have understood you correctly then this program will do as you wish

It reads the first two lines from the file, and replaces the last two fields of the first line with 1 , and the last field from the second line. Then it prints those two lines and copies the rest of the file

The path to the input file is expected as a parameter on the command line

use strict;
use warnings 'all';

my $line1 = <>;
my $line2 = <>;
my ($val) = $line2 =~ /.+\@(.+)/;

$line1 =~ s/\@[^\@]*\@[^\@]*$/\@1 \@$val\n/;

print $line1;
print $line2;

print while <>;

output

5@Comedia   @5@3@2@3@1/2  @3@1.6  @1@2 1/2@1 @4 3/4
3@Melanistic@3@4@2@4@1 1/2@4@2 3/4@3@5    @2 @4 3/4
2@Pure      @4@5@5@5@3 1/2@5@4 3/4@5@8    @3 @6 1/2
4@Profit    @2@2@1@2@1.6  @1@1.6  @2@2 1/2@4 @6 1/2
1@Whammy    @1@1@1@1@1.6  @2@1.6  @4@5 1/2@5 @8 1/4

Answer 2

You can combine all these three commands in one line. Like following:

LENGTH=$(cat sample.txt |awk -F@ 'NR==2{print $NF}') awk -F@ -v l="$length" 'NR==1{$(NF-1)=1;$NF=l;print $0}' OFS=@ sample.txt ; awk -F@ 'NR>1{print $0}' sample.txt

Answer 3

If I have understood you correctly then this awk one liner will do as you wish!!

awk -F@ -v OFS="@" 'NR==1{$12=$12-10; $13=$13-10 " 3/4";}{$11=$11" "; sub(" ", "", $12);}1'

Output:

5@Comedia   @5@3@2@3@1/2  @3@1.6  @1@2 1/2 @1@4 3/4
3@Melanistic@3@4@2@4@1 1/2@4@2 3/4@3@5     @2@4 3/4
2@Pure      @4@5@5@5@3 1/2@5@4 3/4@5@8     @3@6 1/2
4@Profit    @2@2@1@2@1.6  @1@1.6  @2@2 1/2 @4@6 1/2
1@Whammy    @1@1@1@1@1.6  @2@1.6  @4@5 1/2 @5@8 1/4