Use AWK to search fasta file given the second file containing sequence names

Question

I have 2 files. One fasta file contains several fasta sequences, while the other file contains the names of potential sequences that I want to find (example file below).

seq.fasta p>

>Clone_18
GTTACGGGGGACACATTTTCCCTTCCAATGCTGCTTTCAGTGATAAATTGAGCATGATGGATGCTGATAATATCATTCCCGTGT
>Clone_23
GTTACGGGGGGCCGAAAAACACCCAATCTCTCTCTCGCTGAAACCCTACCTGTAATTTGCCTCCGATAGCCTTCCCCGGTGA
>Clone_27-1
GTTACGGGGACCACACCCTCACACATACAAACACAAACACTTCAAGTGACTTAGTGTGTTTCAGCAAAACATGGCTTC
>Clone_27-2
GTTACGGGGACCACACCCTCACACATACAAACACAAACACTTCAAGTGACTTAGTGTGTTTCAGCAAAACATGGCTTCGTTTTGTTCTAGATTAACTATCAGTTTGGTTCTGTTTGTCCTCGTACTGGGTTGTGTCAATGCACAACTT
>Clone_34-1
GTTACGGGGGAATAACAAAACTCACCAACTAACAACTAACTACTACTTCACTTTTCAACTACTTTACTACAATACTAAGAATGAAAACCATTCTCCTCATTATCTTTGCTCTCGCTCTTTTCACAAGAGCTCAAGTCCCTGGCTACCAAGCCATCG
>Clone_34-3
GTTACGGGGGAATAACAAAACTCACCAACTAACAACTAACTACTACTTCACTTTTCAACTACTTTACTACAATACTAAGAATGAAAACCATTCTCCTCATTATCTTTGCTCTCGCTCTTTTCACAAGAGCTCAAGTCCCTGGCTACCAAGCCATCGATATCGCTGAAGCCCAATC
>Clone_44-1
GTTACGGGGGAATCCGAATTCACAGATTCAATTACACCCTAAAATCTATCTTCTCTACTTTCCCTCTCTCCATTCTCTCTCACACACTGTCACACACATCC
>Clone_44-3
GTTACGGGGGAATCCGAATTCACAGATTCAATTACACCCTAAAATCTATCTTCTCTACTTTCCCTCTCTCCATTCTCTCTCACACACTGTCACACACATCCCGGCAGCGCAGCCGTCGTCTCTACCCTTCACCAGGAATAAGTTTATTTTTCTACTTAC

name.txt

Clone_23
Clone_27-1

I want to use AWK to search through the fasta file and get all fasta sequences for the given candidates whose names were saved in another file.

awk 'NR==FNR{a[$1]=$1} BEGIN{RS="\n>"; FS="\n"} NR>FNR {if (match($1,">")) {sub(">","",$1)} for (p in a) {if ($1==p) print ">"$0}}' name.txt seq.fasta

The problem is that I can only extract the sequence of the first candidate in name.txt, for example,

>Clone_23
GTTACGGGGGGCCGAAAAACACCCAATCTCTCTCTCGCTGAAACCCTACCTGTAATTTGCCTCCGATAGCCTTCCCCGGTGA

Can anyone help fix the single line awk command above?

Answer 1

, grep:

grep -Ff name.txt -A1 a.fasta

• -f name.txt name.txt
• -F ,
• A1

, grep:

above_command | grep -v '>'

---

awk :

awk 'NR==FNR{n[$0];next} substr($0,2) in n && getline' name.txt a.fasta

:

# True as long as we are reading the first file, name.txt
NR==FNR {
    # Store the names in the array 'n'
    n[$0]
    next
}

# I use substr() to remove the leading `>` and check if the remaining
# string which is the name is a key of `n`. getline retrieves the next line
# If it succeeds the condition becomes true and awk will print that line
substr($0,2) in n && getline

Answer 2

$ awk 'NR==FNR{n[">"$0];next} f{print f ORS $0;f=""} $0 in n{f=$0}' name.txt seq.fasta
>Clone_23
GTTACGGGGGGCCGAAAAACACCCAATCTCTCTCTCGCTGAAACCCTACCTGTAATTTGCCTCCGATAGCCTTCCCCGGTGA
>Clone_27-1
GTTACGGGGACCACACCCTCACACATACAAACACAAACACTTCAAGTGACTTAGTGTGTTTCAGCAAAACATGGCTTC