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  • caputcastellae
    Junior Member
    • Apr 2010
    • 1

    Extract sequences from a FASTQ file based on another file

    I have two files:

    file 1: fastaq XXGB file
    file 2: list of a few FASTQ ID headers formatted as follows:

    @M01032:192:000000000-AAEFT:1:1101:10100:1004 2:N:0:1
    @M01032:192:000000000-AAEFT:1:1101:10100:1004 1:N:0:1

    Is there an easy way (perl?) to generate a third file with the info (including the ID headers of the targeted sequences (file 2)?

    Thanks!
  • GenoMax
    Senior Member
    • Feb 2008
    • 7142

    #2
    There are probably more elegant ways of doing this but you can try this now. With that said (in tcshell and assuming that your sequences do not wrap around)

    Code:
    $ foreach i (`cat ./file_of_ID_you_need`)
    foreach? grep ^$i -A 3 your_sequence_file >> new_sequence_file
    foreach? end

    Comment

    • gandalf886
      Member
      • Feb 2013
      • 11

      #3
      perhaps this?
      Code:
      grep --no-group-separator -A 3 -Fxf file_2 file_1 > output
      Originally posted by GenoMax View Post
      There are probably more elegant ways of doing this but you can try this now. With that said (in tcshell and assuming that your sequences do not wrap around)

      Code:
      $ foreach i (`cat ./file_of_ID_you_need`)
      foreach? grep ^$i -A 3 your_sequence_file >> new_sequence_file
      foreach? end

      Comment

      • GenoMax
        Senior Member
        • Feb 2008
        • 7142

        #4
        If sequence file is compressed then extending gandalf886's suggestion
        Code:
        $ zmore sample.fastq.gz | grep -A 3 -Fxf  file_of_IDs > new_sequence_file
        or

        Code:
        $ zcat sample.fastq.gz | grep -A 3 -Fxf  file_of_IDs > new_sequence_file

        Comment

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