how to get the ID of the sequence matched from a fasta file

[nmauri]

Hi Everyone!
I am a begginer in Bioinformatics and I need to solve the following problem:
I have a fasta file of protein that looks like this:
>id1
AASEQUENCE1
>id2
AASEQUENCE2
>id3
AASEQUENCE3

I have to match a sequence, for example, AIKA in each sequence and then return the corresponding ids of matches.
Thanks a lot

[dariober]

This has been asked before in different flavours. If you are ok using shell/bash, try this:

awk -v RS=">" 'NR>1 {sub("\n", "\t"); gsub("\n", ""); print ">"$0}' test.fa \
| awk -v FS="\t" '$2 ~ /AIKA/ {sub("\t", "\n"); print $0}'

First awk linearizes the fasta file, second awk captures records containing AIKA and outputs back in fasta format. The original line wrapping is lost though.