How to pipe samtools mileup with varscan trio caller?

Question

[DareDevil]

I have seen piping samtools with varscan as follows

samtools mpileup -f reference.fasta sample1.bam sample2.bam | java -jar VarScan.jar mpileup2snp

But how to pipe the following pipeline for varscan trio

#Generate a three-sample mpileup
samtools mpileup -B -q 1 \
     -f ref.fasta \
     dad.bam mom.bam child.bam > trio.mpileup

#Run VarScan trio
varscan trio \
     trio.mpileup \ #this is input
     trio.mpileup.output \ #this is output
     --min-coverage 10 --min-var-freq 0.20 --p-value 0.05 \ 
     -adj-var-freq 0.05 -adj-p-value 0.15

[Ram]

A lot of tools allow for - to stand in for STDIN. I'm not sure of this, but I think it's a shell feature. Try that.

samtools mpileup -B -q 1 \
     -f ref.fasta \
     dad.bam mom.bam child.bam | varsan trio - trio.mpileuup.output....

More relevant reading: https://unix.stackexchange.com/questions/16357/usage-of-dash-in-place-of-a-filename

[DareDevil]

Update: The command has run successfully. But, there is difference in the output provided by both steps.

Number of de novo without pipe is 66 where as in pipe it 1292.

[Ram]

That's odd. Maybe open an issue/talk to varscan developers? You may want to dig deeper and see what's unique about the 66 captured - maybe they're closer together on the pileup output (I'm just going with a wild guess).

[DareDevil]

Thanks!!. It has started running. I'll compare the ouputs of both command and verify