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samtools-faidx(1)	     Bioinformatics tools	     samtools-faidx(1)

NAME
       samtools	faidx -	indexes	or queries regions from	a fasta	file

SYNOPSIS
       samtools	faidx ref.fasta	[region1 [...]]

DESCRIPTION
       Index  reference	 sequence  in  the FASTA format	or extract subsequence
       from indexed reference sequence.	If no region is	specified, faidx  will
       index  the  file	and create <ref.fasta>.fai on the disk.	If regions are
       specified, the subsequences will	be retrieved and printed to stdout  in
       the FASTA format.

       The  input  and output can be files compressed in the BGZF format. When
       output is compressed, the default compression level is 4.

       The sequences in	the input file should all have	different  names.   If
       they do not, indexing will emit a warning about duplicate sequences and
       retrieval  will	only produce subsequences from the first sequence with
       the duplicated name.

       FASTQ files can be read and indexed by  this  command.	Without	 using
       --fastq any extracted subsequence will be in FASTA format.

OPTIONS
       -o, --output FILE
	       Write  FASTA  to	 file  rather  than to stdout. With .gz, .bgz,
	       .bgzf file extensions the output	will be	BGZF compressed.

       -n, --length INT
	       Length for FASTA	sequence line wrapping.	 If zero,  this	 means
	       do  not	line  wrap.   Defaults to the line length in the input
	       file.

       -c, --continue
	       Continue	working	if a non-existent region is requested.

       -r, --region-file FILE
	       Read regions from a file. Format	is chr:from-to,	one per	line.

       -f, --fastq
	       Read FASTQ files	and output extracted sequences in  FASTQ  for-
	       mat.  Same as using samtools fqidx.

       -i, --reverse-complement
	       Output  the  sequence as	the reverse complement.	 When this op-
	       tion is used, "/rc" will	be appended to the sequence names.  To
	       turn this off or	change the string appended,  use  the  --mark-
	       strand option.

       --mark-strand TYPE
	       Append strand indicator to sequence name.  TYPE can be one of:

	       rc     Append  '/rc' when writing the reverse complement.  This
		      is the default.

	       no     Do not append anything.

	       sign   Append '(+)' for forward strand  or  '(-)'  for  reverse
		      complement.   This  matches the output of	"bedtools get-
		      fasta -s".

	       custom,<pos>,<neg>
		      Append string <pos> to names when	 writing  the  forward
		      strand  and  <neg>  when	writing	 the  reverse  strand.
		      Spaces are preserved, so it is possible to move the  in-
		      dicator into the comment part of the description line by
		      including	 a  leading  space  in	the  strings <pos> and
		      <neg>.

       --fai-idx FILE
	       Read/Write to specified index file.

       --gzi-idx FILE
	       Read/Write to specified compressed file index  (used  with  .gz
	       files).

       -h, --help
	       Print help message and exit.

       --output-fmt-option OPT=VAL
	       Set the output format options, level=0..9 for compression level
	       0 to 9.

       -@, --threads N
	       Set  the	 number	 of extra threads for operations on compressed
	       files.

AUTHOR
       Written by Heng Li, with	modifications by Andrew	 Whitwham  and	Robert
       Davies, all from	the Sanger Institute.

SEE ALSO
       samtools(1), samtools-fasta(1), samtools-fqidx(1), samtools-fastq(1)

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

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

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