Use mruby to evaluate expressions in samtools!

git clone https://github.com/kojix2/samtools-mruby
make
samtools/samtools tanuki # check if it works

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　Tanuki in mruby (3.3.0)

Rake is required to build mruby. If you are using conda to install Ruby, set the LD environment variable:

rake LD=/usr/bin/gcc MRUBY_CONFIG=$(pwd)/mruby_build_config.rb -f $(pwd)/mruby/Rakefile

The samtools-mruby project allows you to use mruby expressions to manipulate and analyze BAM files. The available variables include:

• endpos: Alignment end position (1-based)
• flags: Combined FLAG field
  • paired, proper_pair, unmap, munmap, reverse, mreverse, read1, read2, secondary, qcfail, dup, supplementary
  • These can be used with or without the ? suffix, e.g., paired and paired? are equivalent.
• hclen: Number of hard clipped bases
• library: Library (LB header via RG)
• mapq: Mapping quality
• mpos: Synonym for pnext
• mrefid: Mate reference number (0 based)
• mrname: Synonym for rnext
• ncigar: Number of CIGAR operations
• pnext: Mate's alignment position (1-based)
• pos: Alignment position (1-based)
• qlen: Alignment length: no. query bases
• qname: Query name
• qual: Quality values (raw, 0-based)
• refid: Integer reference number (0 based)
• rlen: Alignment length: no. reference bases
• rname: Reference name
• rnext: Mate's reference name
• sclen: Number of soft clipped bases
• seq: Sequence
• tlen: Template length (insert size)
• tag: XX tag value

These variables enable detailed data manipulation and analysis.

• Basic Usage: Output read name and sequence in green.

  samtools view -E 'puts qname.ljust(13) + seq.green' htslib/test/colons.bam

• Pattern Highlighting: Use regular expressions.

  samtools view -E 'puts qname.ljust(13) + seq.gsub(/CG/, &:red)' htslib/test/colons.bam

• Flag Methods: Access SAM flag information. Flag methods can be used with or without the ? suffix. For example, paired and paired? are equivalent.

  samtools view -E 'puts "#{qname} is paired" if paired?' example.bam

• Tag Access: Retrieve BAM tags.

  samtools view -E 'puts "NM:#{tag("NM")}" if tag("NM")' example.bam

• Custom Filtering: Use expressions for filtering.

  samtools view -E 'puts qname if prpper_pair?' example.bam
  # samtools view -E 'puts qname if flags & 0x2 != 0' example.bam

• Local: Defined inside expressions, do not persist.
• Global: Defined with $, persist across records.

Example to count mapped reads:

samtools view -E '$count ||= 0; $count += 1 unless unmap?; END { puts $count }' example.bam

The samtools-mruby project integrates mruby into samtools, allowing for enhanced functionality through mruby expressions. This integration includes:

• Makefile Modifications: Added support for mruby by including MRBDIR, MRB_CPPFLAGS, and MRB_LDFLAGS. Updated object files list to include tanuki.o and sam_view_mruby.o.
• bamtk.c: Introduced a new tanuki command, which displays a tanuki using mruby.
• sam_view.c: Added support for evaluating mruby expressions with a new mruby_expr field in settings. Integrated mruby initialization and finalization.
• New Files:
  • sam_view_mruby.c: Implements methods for interacting with BAM records using mruby.
  • sam_view_mruby.h: Header file for sam_view_mruby.c.
  • tanuki.c: Contains the implementation for the tanuki command.

To see changes made to the original samtools repository:

git -C samtools diff origin/develop...origin/mruby

• The mruby and htslib directories are submodules.
  • mruby-terminal-color
  • mruby-regexp-pcre
• samtools is based on the mruby branch of the kojix2 repository.
• The tanuki subcommand distinguishes between standard and mruby-enhanced samtools.

Send pull requests to the mruby branch of my samtools repository.

• MIT License
• This tool was created actively using code generators such as ChatGPT and Copilot.

• bcftools-mruby