Provided by: samtools_1.10-3_amd64 
NAME
samtools flagstat - counts the number of alignments for each FLAG type
SYNOPSIS
samtools flagstat in.sam|in.bam|in.cram
DESCRIPTION
Does a full pass through the input file to calculate and print statistics to stdout.
Provides counts for each of 13 categories based primarily on bit flags in the FLAG field. Each category
in the output is broken down into QC pass and QC fail. In the default output format, these are presented
as "#PASS + #FAIL" followed by a description of the category.
The first row of output gives the total number of reads that are QC pass and fail (according to flag bit
0x200). For example:
122 + 28 in total (QC-passed reads + QC-failed reads)
Which would indicate that there are a total of 150 reads in the input file, 122 of which are marked as QC
pass and 28 of which are marked as "not passing quality controls"
Following this, additional categories are given for reads which are:
secondary
0x100 bit set
supplementary
0x800 bit set
duplicates
0x400 bit set
mapped 0x4 bit not set
paired in sequencing
0x1 bit set
read1 both 0x1 and 0x40 bits set
read2 both 0x1 and 0x80 bits set
properly paired
both 0x1 and 0x2 bits set and 0x4 bit not set
with itself and mate mapped
0x1 bit set and neither 0x4 nor 0x8 bits set
singletons
both 0x1 and 0x8 bits set and bit 0x4 not set
And finally, two rows are given that additionally filter on the reference name (RNAME), mate
reference name (MRNM), and mapping quality (MAPQ) fields:
with mate mapped to a different chr
0x1 bit set and neither 0x4 nor 0x8 bits set and MRNM not equal to RNAME
with mate mapped to a different chr (mapQ>=5)
0x1 bit set and neither 0x4 nor 0x8 bits set and MRNM not equal to RNAME and
MAPQ >= 5
ALTERNATIVE OUTPUT FORMATS
The -O option can be used to select two alternative formats for the output.
Using -O tsv selects a tab-separated values format that can easily be imported into spreadsheet software.
In this format the first column contains the values for QC-passed reads, the second column has the values
for QC-failed reads and the third contains the category names.
Using -O json generates an ECMA-404 JSON data interchange format object <https://www.json.org/>. The
top-level object contains two named objects QC-passed reads and QC-failed reads. These contain the
various categories listed above as names and the corresponding count as value.
For the default format, the mapped, properly paired, and singletons show the count as a percentage of the
total number of QC-passed or QC-failed reads after the category name. For example:
32 + 0 mapped (94.12% : N/A)
In the tsv and json formats, these percentages are listed in separate categories mapped %, properly
paired %, and singletons %. If the percentage cannot be calculated (because the total is zero) then in
the default and tsv formats it will be reported as `N/A'. In the json format, it will be reported as a
JSON `null' value.
OPTIONS
-@ INT Set number of additional threads to use when reading the file.
-O FORMAT Set the output format. FORMAT can be set to `default', `json' or `tsv' to select the default,
JSON or tab-separated values output format. If this option is not used, the default format
will be selected.
AUTHOR
Written by Heng Li from the Sanger Institute.
SEE ALSO
samtools(1), samtools-idxstats(1), samtools-stats(1)
Samtools website: <http://www.htslib.org/>
samtools-1.10 6 December 2019 samtools-flagstat(1)