I wish to call SNPs using SAMtools mpileup function.
I first map my Illumina paired end reads to the reference using Bowtie and then 
I have custom scripts that filter out non-uniquely mapping reads. To do this I 
rely on the absence of XS to indicate a uniquely mapped read.

However, this creates a potential problem as the SAM flags are often no longer 
meaningful.
Eg. Originally I have two reads that are paired and both map
Forward read flag 83
Reverse read flag 163
If Forward read is not uniquely mapping then I remove this from the sam file, 
leaving Reverse read intact. The flag of Reverse read is not changed and 
therefore now falsely indicates it has a mapped pair. This isn't a problem if 
my downstream programs do not use the flag.

Therefore, I wanted to check, does the mpileup function read/use the flags in 
the sam file?

If so, is there another way to only use uniquely mapping reads to call SNPs.

Thanks very much
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