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samtools-fqidx(1)	     Bioinformatics tools	     samtools-fqidx(1)

NAME
       samtools	fqidx -	Indexes	or queries regions from	a fastq	file

SYNOPSIS
       samtools	fqidx ref.fastq	[region1 [...]]

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

       The input file can be compressed	in the BGZF format.

       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.

       samtools	 fqidx	should only be used on fastq files with	a small	number
       of entries.  Trying to use it on	a file containing  millions  of	 short
       sequencing  reads  will	produce	 an index that is almost as big	as the
       original	file, and searches using the index will	be very	slow and use a
       lot of memory.

OPTIONS
       -o, --output FILE
	       Write FASTQ to file rather than to stdout.

       -n, --length INT
	       Length for FASTQ	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.

       -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.

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

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

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

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

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