Provided by: samtools_1.13-4_amd64 
NAME
samtools-sort - sorts SAM/BAM/CRAM files
SYNOPSIS
samtools sort [-l level] [-u] [-m maxMem] [-o out.bam] [-O format] [-M] [-K kmerLen] [-n]
[-t tag] [-T tmpprefix] [-@ threads] [in.sam|in.bam|in.cram]
DESCRIPTION
Sort alignments by leftmost coordinates, or by read name when -n is used. An appropriate
@HD-SO sort order header tag will be added or an existing one updated if necessary.
The sorted output is written to standard output by default, or to the specified file
(out.bam) when -o is used. This command will also create temporary files tmpprefix.%d.bam
as needed when the entire alignment data cannot fit into memory (as controlled via the -m
option).
Consider using samtools collate instead if you need name collated data without a full
lexicographical sort.
Note that if the sorted output file is to be indexed with samtools index, the default
coordinate sort must be used. Thus the -n and -t options are incompatible with samtools
index.
OPTIONS
-K INT Sets the kmer size to be used in the -M option. [20]
-l INT Set the desired compression level for the final output file, ranging from 0
(uncompressed) or 1 (fastest but minimal compression) to 9 (best compression
but slowest to write), similarly to gzip(1)'s compression level setting.
If -l is not used, the default compression level will apply.
-u Set the compression level to 0, for uncompressed output. This is a synonym for
-l 0.
-m INT Approximately the maximum required memory per thread, specified either in bytes
or with a K, M, or G suffix. [768 MiB]
To prevent sort from creating a huge number of temporary files, it enforces a
minimum value of 1M for this setting.
-M Sort unmapped reads (those in chromosome "*") by their sequence minimiser
(Schleimer et al., 2003; Roberts et al., 2004), also reverse complementing as
appropriate. This has the effect of collating some similar data together,
improving the compressibility of the unmapped sequence. The minimiser kmer
size is adjusted using the -K option. Note data compressed in this manner may
need to be name collated prior to conversion back to fastq.
Mapped sequences are sorted by chromosome and position.
-n Sort by read names (i.e., the QNAME field) rather than by chromosomal
coordinates.
-t TAG Sort first by the value in the alignment tag TAG, then by position or name (if
also using -n).
-o FILE Write the final sorted output to FILE, rather than to standard output.
-O FORMAT Write the final output as sam, bam, or cram.
By default, samtools tries to select a format based on the -o filename
extension; if output is to standard output or no format can be deduced, bam is
selected.
-T PREFIX Write temporary files to PREFIX.nnnn.bam, or if the specified PREFIX is an
existing directory, to PREFIX/samtools.mmm.mmm.tmp.nnnn.bam, where mmm is
unique to this invocation of the sort command.
By default, any temporary files are written alongside the output file, as
out.bam.tmp.nnnn.bam, or if output is to standard output, in the current
directory as samtools.mmm.mmm.tmp.nnnn.bam.
-@ INT Set number of sorting and compression threads. By default, operation is
single-threaded.
--no-PG Do not add a @PG line to the header of the output file.
Ordering Rules
The following rules are used for ordering records.
If option -t is in use, records are first sorted by the value of the given alignment tag,
and then by position or name (if using -n). For example, “-t RG” will make read group the
primary sort key. The rules for ordering by tag are:
• Records that do not have the tag are sorted before ones that do.
• If the types of the tags are different, they will be sorted so that single character
tags (type A) come before array tags (type B), then string tags (types H and Z), then
numeric tags (types f and i).
• Numeric tags (types f and i) are compared by value. Note that comparisons of
floating-point values are subject to issues of rounding and precision.
• String tags (types H and Z) are compared based on the binary contents of the tag using
the C strcmp(3) function.
• Character tags (type A) are compared by binary character value.
• No attempt is made to compare tags of other types — notably type B array values will
not be compared.
When the -n option is present, records are sorted by name. Names are compared so as to
give a “natural” ordering — i.e. sections consisting of digits are compared numerically
while all other sections are compared based on their binary representation. This means
“a1” will come before “b1” and “a9” will come before “a10”. Records with the same name
will be ordered according to the values of the READ1 and READ2 flags (see flags).
When the -n option is not present, reads are sorted by reference (according to the order
of the @SQ header records), then by position in the reference, and then by the REVERSE
flag.
Note
Historically samtools sort also accepted a less flexible way of specifying the final and
temporary output filenames:
samtools sort [-f] [-o] in.bam out.prefix
This has now been removed. The previous out.prefix argument (and -f option, if any)
should be changed to an appropriate combination of -T PREFIX and -o FILE. The previous -o
option should be removed, as output defaults to standard output.
AUTHOR
Written by Heng Li from the Sanger Institute with numerous subsequent modifications.
SEE ALSO
samtools(1), samtools-collate(1), samtools-merge(1)
Samtools website: <http://www.htslib.org/>