Parallel xargs by Chr
This applet slices a BAM file by canonical chromosome then performs a parallelized samtools view -c using xargs. Type man xargs for general usage information.
How is the SAMtools dependency provided?
The SAMtools compiled binary is placed directory in the
<applet dir>/resources directory. Any files found in the resources/ directory will be uploaded so that they will be present in the root directory of the worker. In our case:1
├── Applet dir
2
│ ├── src
3
│ ├── dxapp.json
4
│ ├── resources
5
│ ├── usr
6
│ ├── bin
7
│ ├── < samtools binary >
Copied!
When this applet is run on a worker, the
resources/ folder will be placed in the worker’s root directory /:1
/
2
├── usr
3
│ ├── bin
4
│ ├── < samtools binary >
5
├── home
6
│ ├── dnanexus
Copied!
/usr/bin is part of the $PATH variable, so in our script, we can reference the samtools command directly, as in samtools view -c ...Parallel Run
Splice BAM
First, we download our BAM file and slice it by canonical chromosome, writing the
*bam file names to another file.In order to split a BAM by regions, we need to have a
*.bai index. You can either create an app(let) which takes the *.bai as an input or generate a *.bai in the applet. In this tutorial, we generate the *.bai in the applet, sorting the BAM if necessary.1
dx download "${mappings_bam}"
2
3
indexsuccess=true
4
bam_filename="${mappings_bam_name}"
5
samtools index "${mappings_bam_name}" || indexsuccess=false
6
if [[ $indexsuccess == false ]]; then
7
samtools sort -o "${mappings_bam_name}" "${mappings_bam_name}"
8
samtools index "${mappings_bam_name}"
9
bam_filename="${mappings_bam_name}"
10
fi
11
12
13
chromosomes=$(samtools view -H "${bam_filename}" | grep "\@SQ" | awk -F '\t' '{print $2}' | awk -F ':' '{if ($2 ~ /^chr[0-9XYM]+$|^[0-9XYM]/) {print $2}}')
14
15
for chr in $chromosomes; do
16
samtools view -b "${bam_filename}" "${chr}" -o "bam_${chr}."bam
17
echo "bam_${chr}.bam"
18
done > bamfiles.txt
Copied!
Xargs SAMtools view
In the previous section, we recorded the name of each sliced BAM file into a record file. Now we will perform a
samtools view -c on each slice using the record file as input.1
counts_txt_name="${mappings_bam_prefix}_count.txt"
2
3
sum_reads=$(<bamfiles.txt xargs -I {} samtools view -c $view_options '{}' | awk '{s+=$1} END {print s}')
4
echo "Total Count: ${sum_reads}" > "${counts_txt_name}"
Copied!
Upload results
The results file is uploaded using the standard bash process:
- 1.Upload a file to the job execution’s container.
- 2.Provide the DNAnexus link as a job’s output using the script
dx-jobutil-add-output <output name>1counts_txt_id=$(dx upload "${counts_txt_name}" --brief)2dx-jobutil-add-output counts_txt "${counts_txt_id}" --class=fileCopied!
Last modified 2yr ago
Export as PDF
Copy link