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samtools-reference(1)	     Bioinformatics tools	 samtools-reference(1)

NAME
       samtools	reference - extracts an	embedded reference from	a CRAM file

SYNOPSIS
       samtools	reference [-q] [-r region] [-o out.fa] in.cram

DESCRIPTION
       Creates the reference from aligned data using either the	MD:Z auxiliary
       tags  or	 an  embedded reference	in a CRAM file.	 The output is a FASTA
       file.

       For the embedded	reference mode (-e) this operation is fast,  but  only
       works  on  CRAMs	 produced using	--output-fmt-option embed_ref=1.  Note
       this may	not be the complete reference used.  Each CRAM slice will hold
       the entire reference that spans the slice coordinates, but gaps in cov-
       erage can lead to gaps between slices.  However this  reference	should
       be suitable for passing into a CRAM decode (samtools view -T ref.fa).

       For  SAM/BAM  files  or CRAMs without reference,	using the MD:Z tag may
       also produce an incomplete reference.  Unlike embedded reference,  this
       reference  may  not  be sufficient for decoding a CRAM file as the CRAM
       slice headers store the MD5sum of the portion of	reference  than	 spans
       that  slice,  but the slice may not have	100% coverage leading to Ns in
       the computed reference.	However	it should still	be possible to	decode
       such  CRAMs  by	ignoring  the  md5 mismatches using e.g. samtools view
       --input-fmt-option ignore_md5=1.

OPTIONS
       -e      Enable CRAM embedded reference mode.

       -q      Enables quiet mode and will produce no output.	By  default  a
	       line  per reference is reporting	describing the percentage with
	       non-N bases.

       -r region
	       Specifies a single region to produce the	 reference  from.   If
	       specified, an index file	must be	present.

       -o FILE Write  the  FASTA  records to FILE.  By default this is sent to
	       stdout.

       -@ INT  The number of BAM/CRAM decompression threads to use in addition
	       to the main thread [0].

	       Note this does not multi-thread the main	 reference  generation
	       steps, so scaling may be	capped by 2 or 3 threads, depending on
	       the  data.   It will also not affect the	-e option for CRAM em-
	       bedded reference, although this is already the fastest method.

AUTHOR
       Written by James	Bonfield from the Sanger Institute.

SEE ALSO
       samtools(1)

       Samtools	website: <http://www.htslib.org/>

samtools-1.21		       12 September 2024	 samtools-reference(1)

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