Question

I’m searching for a solution of this problem:
I have a file (tab-separated) like I show in the following blockquote. As you can see
there are lines that match the first part (Bold fields).

chr4 164440449 165354407 G1 P8002-51-75
chr1 220871675 220962596 G2 P2368-132-84
chr1 220871675 220962596 G2 P2369-152-116
chr1 220871675 220962596 G2 P2371-180-82
chr1 220871675 220962596 G2 P2372-223-129
chr1 220871675 220962596 G2 P2373-153-96
chr1 220871675 220962596 G2 P2370-104-78
chr5 126198405 126416440 G3 P9333-135-146
chr5 126198405 126416440 G3 P9334-151-116

Using AWK or PERL how could I manage to obtain the following output conserving the tab-separated format??? The general concept is to try to unify lines according to it’s first part, and append the last field

chr4 164440449 165354407 G1 P8002-51-75
chr1 220871675 220962596 G2 P2368-132-84 P2369-152-116 P2371-180-82 P2372-223-129 P2373-153-96 P2370-104-78
chr5 126198405 126416440 G3 P9333-135-146 P9334-151-116

The general concept is to try to unify lines according to it’s first part, and append the last field

Answer 1

One way using perl:

perl -ane '
    ## Save all fields but the last one as the key to compare between rows.
    $key = join qq|\t|, @F[ 0 .. $#F - 1 ];

    ## In first line or when current key is equal to previous key, save last
    ## field in an array and stop processing current row.
    if ( $. == 1 || $key eq $pkey ) {
        $pkey = $key;
        push @value, $F[ $#F ];
        next unless eof;
    }

    ## At this point, keys between rows are different, so print previous
    ## key with its values and begin to save the new one.
    printf qq|%s\n|, join qq|\t|, $pkey, @value;
    @value = ();
    push @value, $F[ $#F ];

    ## Exception: Last line with a new key, print it.
    if ( eof && $pkey ne $key ) {
    printf qq|%s\n|, join qq|\t|, $key, @value;
    }

    ## Save previous key.
    $pkey = $key;

' infile

Assuming infile with the data of your question, output will be:

chr4    164440449       165354407       G1      P8002-51-75
chr1    220871675       220962596       G2      P2368-132-84    P2369-152-116   P2371-180-82    P2372-223-129   P2373-153-96    P2370-104-78
chr5    126198405       126416440       G3      P9333-135-146   P9334-151-116