How to split awk field correctly - awk

Question

I have a file (test.bed) that looks like this (which might not be tab-seperated):
chr1 10002 10116 id=1;frame=0;strand=+; 0 +
chr1 10116 10122 id=2;frame=0;strand=+; 0 +
chr1 10122 10128 id=3;frame=0;strand=+; 0 +
chr1 10128 10134 id=4;frame=0;strand=+; 0 +
chr1 10134 10140 id=5;frame=0;strand=+; 0 +
chr1 10140 10146 id=6;frame=0;strand=+; 0 +
chr1 10146 10182 id=7;frame=0;strand=+; 0 +
chr1 10182 10188 id=8;frame=0;strand=+; 0 +
chr1 10188 10194 id=9;frame=0;strand=+; 0 +
chr1 10194 10200 id=10;frame=0;strand=+; 0 +
I want to produce the following output (which should be tab-seperated):
chr1 10002 10116 id=1 0 +
chr1 10116 10122 id=2 0 +
chr1 10122 10128 id=3 0 +
chr1 10128 10134 id=4 0 +
chr1 10134 10140 id=5 0 +
chr1 10140 10146 id=6 0 +
chr1 10146 10182 id=7 0 +
chr1 10182 10188 id=8 0 +
chr1 10188 10194 id=9 0 +
chr1 10194 10200 id=10 0 +
I have tried with the following code:
awk 'OFS="\t" split ($0, a, ";"){print a[1],$5,$6}' test.bed
But then I get:
chr1 10002 10116 id=1 40 4+
chr1 10116 10122 id=2 40 4+
chr1 10122 10128 id=3 40 4+
chr1 10128 10134 id=4 40 4+
chr1 10134 10140 id=5 40 4+
chr1 10140 10146 id=6 40 4+
chr1 10146 10182 id=7 40 4+
chr1 10182 10188 id=8 40 4+
chr1 10188 10194 id=9 40 4+
chr1 10194 10200 id=10 40 4+
What am I doing wrong? Somehow the number '4' is added to the last two fields. I thought the number '4' somehow might have something to do with splitting in the 4th field, however, I tried producing a similar file where it was the 3rd field that was split, and still got the number '4' added to the last two fields. I am rather new to 'awk' so I guess it is an error in the syntax. Any help would be appreciated.

Answer 1

If you set your field separator as whitespace or semi-columns you won't have to handle the splitting yourself:
$ awk '{print $1,$2,$3,$4,$8,$9}' FS='[[:space:]]+|;' OFS='\t' file
chr1 10002 10116 id=1 0 +
chr1 10116 10122 id=2 0 +
chr1 10122 10128 id=3 0 +
chr1 10128 10134 id=4 0 +
chr1 10134 10140 id=5 0 +
chr1 10140 10146 id=6 0 +
chr1 10146 10182 id=7 0 +
chr1 10182 10188 id=8 0 +
chr1 10188 10194 id=9 0 +
chr1 10194 10200 id=10 0 +
As for what you are doing wrong in:
awk 'OFS="\t" split ($0, a, ";"){print a[1],$5,$6}'
The syntax of awk is condition{block} and setting the value of OFS and splitting is not a conditional. They are statements that should be inside the block.
However you really don't need to set the value of OFS on every line so it should be initialized only once. You can do this using the -v option, in the BEGIN block or after the script.
Valid alternatives:
$ awk -v OFS='\t' '{split($0,a,";");print a[1],$5,$6}' file
$ awk 'BEGIN{OFS="\t"}{split($0,a,";");print a[1],$5,$6}' file
$ awk '{split ($0,a,";");print a[1],$5,$6}' OFS='\t' file

Answer 2

Try this :
awk -F\; '{print $1,$4}' test.bed