Cat until certain nb occurence in bash

Question

I have a file such as :

@SRR9110374.1 1/1
GAGTATAAAGAAGAAAGTAAATCTCGGTTCGTCTCTTCATCGAGAGAAATGTCGACGAGAAAAAAAAAACAAGGGCTCATTTAAAGCCTTTCAAATCCT
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
@SRR9110374.2 2/1
ATATGGAACAAGTTAAAAAAAATAAAAAGCAAAGAAATAATGTTTTGTCATCGAAAGTGTCGACATAAAAACAGGTTGGCATCTGGCCTGGTATCTCA
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF<BFFFFFFF<FFFFFFFFFFF
@SRR9110374.3 3/1
NTATAACCGTATCAAAGAAGTTTACCCCGAGAGAAGCACGCAGTTTCCCACAGGTAATTTTCTCACAAGCGAGAGAAACATCATACCGCAATCAGGAAC
+
#<<BBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFBFFFFFFFFFFFFFF
@SRR9110374.4 4/1
GATAAAGAATATAGCTATGTATAGCCGGGATATATTAAGTGATTGAAATATCTCTTAGAAATCCATAGAATAGTAGTGTATCGAATAGGAGGAAGCGAAA
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
@SRR9110374.5 5/1
CTTCCAATGCTTGCCAAAGTTCATTGTCGTTGTAATTATCGAAAGGATCTAAATTCTTTCTCAACGAACCCGAGAATAGGAAGGGTTCTTGAGGAATTAT
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF/FFFFFFFFFFFFFFFFFFBFFF/FFF
@SRR9110374.6 6/1
ACCGATAATCTTTCCTTCTCAAGAATTTTGTTAATATTCCACATTTTTAAATAGATTTCATTTCTCTCTCTCTTTCTCTCTCTTTTTCTTGTCCTCGATG
+
BBBBBFFFFFFFFFFFFFFFFFFFFFBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFBFFBFFFF///FF
@SRR9110374.7 7/1
GTTGTGCTGAGAATGTTAATAAATTACAAAATGTTATCACTAACTTGGAAATATTCGAATCGACAGATATCGCGTTTGTCGTGTTGTATTAATATATTC
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
@SRR9110374.8 8/1
GTCATAGAACGGGGGAGGGGAGGAAGAAGAAAGGAAGGGAAAAAAACGAGAGAGAGAGAGGGGATTACGCTCGCCGTTCGAATCGTTAGGCGTCCGTTT
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFBFFFFFFFFFFFFFFFFFFBBFBBFF
@SRR9110374.9 9/1
AATTATTATTTAATCGACGCGTCTATCGATAAATCATCCTCGAATGCTAAGCAAAACTGAACTTCCGCAAATATTGCACACGAAACGTTGAAACAAAG
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF

and I would like to cat the content untill the Xth occurence savec in the Nb_occurence variable into a new file.

I tried :

Nb_occurence=4
cat file | awk 'BEGIN{ found=0} /@/{found=found+1} {if ( found < $Nb_occurence ) print }'

I should get :

@SRR9110374.1 1/1
GAGTATAAAGAAGAAAGTAAATCTCGGTTCGTCTCTTCATCGAGAGAAATGTCGACGAGAAAAAAAAAACAAGGGCTCATTTAAAGCCTTTCAAATCCT
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
@SRR9110374.2 2/1
ATATGGAACAAGTTAAAAAAAATAAAAAGCAAAGAAATAATGTTTTGTCATCGAAAGTGTCGACATAAAAACAGGTTGGCATCTGGCCTGGTATCTCA
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF<BFFFFFFF<FFFFFFFFFFF
@SRR9110374.3 3/1
NTATAACCGTATCAAAGAAGTTTACCCCGAGAGAAGCACGCAGTTTCCCACAGGTAATTTTCTCACAAGCGAGAGAAACATCATACCGCAATCAGGAAC
+
#<<BBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFBFFFFFFFFFFFFFF
@SRR9110374.4 4/1
GATAAAGAATATAGCTATGTATAGCCGGGATATATTAAGTGATTGAAATATCTCTTAGAAATCCATAGAATAGTAGTGTATCGAATAGGAGGAAGCGAAA
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF

Ps: The real file is very huge so i I should get a method adapted to that it would be nice.

RavinderSingh13 · Answer 1 · 2019-12-16T14:11:50.550

Could you please try following.

Nb_occurence=4
awk -v nb_occur="$Nb_occurence" '
BEGIN{
  occur=0
}
/@/{
  occur++
}
occur>nb_occur{
  exit
}
occur
' Input_file

Ps: The real file is very huge so i I should get a method adapted to that it would be nice.

To make Input_file reading faster:

To FASTER your processing of Input_file I have used exit so once your mentioned number of occurrences are done with reading it will ASAP come out of Input_file, since we need NOT to read it further and thus it should be FASTER than your solution.

score 2 · Answer 2 · answered Dec 16 '19 at 14:01

2

You should rewrite your awk on this way:

awk -v occurence=$Nb_occurence 'BEGIN{ found=0} /@/{found=found+1} {if ( found < occurence ) print }' file

And you do not need cat, awk can read the file

answered Dec 16 '19 at 14:01

Romeo Ninov

5,508
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1

Doing so, you will read entire file, this could become harmfull if file is huge! Have a look at [RavinderSingh13's solution](https://stackoverflow.com/a/59358192/1765658)! – F. Hauri Dec 16 '19 at 14:09
Right. But this is the way of OP. I just tune his/her solution. – Romeo Ninov Dec 16 '19 at 14:11

score 2 · Accepted Answer · answered Dec 16 '19 at 14:09

Yet another awk:

$ awk -v n=4 '/@/&&!n--{exit}1' file

Output:

@SRR9110374.1 1/1
GAGTATAAAGAAGAAAGTAAATCTCGGTTCGTCTCTTCATCGAGAGAAATGTCGACGAGAAAAAAAAAACAAGGGCTCATTTAAAGCCTTTCAAATCCT
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
@SRR9110374.2 2/1
ATATGGAACAAGTTAAAAAAAATAAAAAGCAAAGAAATAATGTTTTGTCATCGAAAGTGTCGACATAAAAACAGGTTGGCATCTGGCCTGGTATCTCA
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF<BFFFFFFF<FFFFFFFFFFF
@SRR9110374.3 3/1
NTATAACCGTATCAAAGAAGTTTACCCCGAGAGAAGCACGCAGTTTCCCACAGGTAATTTTCTCACAAGCGAGAGAAACATCATACCGCAATCAGGAAC
+
#<<BBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFBFFFFFFFFFFFFFF
@SRR9110374.4 4/1
GATAAAGAATATAGCTATGTATAGCCGGGATATATTAAGTGATTGAAATATCTCTTAGAAATCCATAGAATAGTAGTGTATCGAATAGGAGGAAGCGAAA
+
BBBBBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF

Explained:

$ awk -v n=4 '    # -v variable=value is the way to introduce values to awk from the shell
/@/ && !n-- {     # when @ met (n+1)th time
    exit          # ... exit
}1' file          # output

Cat until certain nb occurence in bash

3 Answers3