Delete all text after a specific occurrence in a string using bash

Question

I have a sequence:

MALYYDHQIEAPDAAGSPSFISWHPVHPFLAVAYISTTSTGSVDIYLEQGECVPDTHVERPFRVASLCWHPTRLVLAVGWETGEVTVFNKQDKEQHTMPLTHTADITVLRWSPSGNCLLSGDRLGVLLLWRLDQRGRVQGTPLLKHEYGKHLTHCIFRLPPPGEDLVQLAKAAVSGDEKALDMFNWKKSSSGSLLKMGSHEGLLFFVSLMDGTVHYVDEKGKTTQVVSADSTIQMLFYMEKREALVVVTENLRLSLYTVPPEGKAEEVMKVKLSGKTGRRADIALIEGSLLVMAVGEAALRFWDIERGENYILSPDEKFGFEKGENMNCVCYCKVKGLLAAGTDRGRVAMWRKVPDFLGSPGAEGKDRWALQTPTELQGNITQIQWGSRKNLLAVNSVISVAILSERAMSSHFHQQVAAMQVSPSLLNVCFLSTGVAHSLRTDMHISGVFATKDAVAVWNGRQVAIFELSGAAIRSAGTFLCETPVLAMHEENVYTVESNRVQVRTWQGTVKQLLLFSETEGNPCFLDICGNFLVVGTDLAHFKSFDLSRREAKAHCSCRSLAELVPGVGGIASLRCSSSGSTISILPSKADNSPDSKICFYDVEMDTVTVFDFKTGQIDRRETLSFNEQETNKSHLFVDEGLKNYVPVNHFWDQSEPRLFVCEAVQETPRSQPQSANGQPQDGRAGPAADVLILSFFISEEHGFLLHESFPRPATSHSLLGMEVPYYYFTRKPEEADREDEVEPGCHHIPQMVSRRPLRDFVGLEDCDKATRDAMLHFSFFVTIGDMDEAFKSIKLIKSEAVWENMARMCVKTQRLDVAKVCLGNMGHARGARALREAEQEPELEARVAVLATQLGMLEDAEQLYRKCKRHDLLNKFYQAAGRWQEALQVAEHHDRVHLRSTYHRYAGHLEASADCSRALSYYEKSDTHRFEVPRMLSEDLPSLELYVNKMKDKTLWRWWAQYLESQGEMDAALHYYELARDHFSLVRIHCFQGNVQKAAQIANETGNLAASYHLARQYESQEEVGQAVHFYTRAQAFKNAIRLCKENGLDDQLMNLALLSSPEDMIEAARYYEEKGVQMDRAVMLYHKAGHFSKALELAFATQQFVALQLIAEDLDETSDPALLARCSDFFIEHSQYERAVELLLAARKYQEALQLCLGQNMSITEEMAEKMTVAKDSSDLPEESRRELLEQIADCCMRQGSYHLATKKYTQAGNKLKAMRALLKSGDTEKITFFASVSRQKEIYIMAANYLQSLDWRKEPEIMKNIIGFYTKGRALDLLAGFYDACAQVEIDEYQNYDKAHGALTEAYKCLAKAKAKSPLDQETRLAQLQSRMALVKRFIQARRTYTEDPKESIKQCELLLEEPDLDSTIRIGDVYGFLVEHYVRKEEYQTAYRFLEEMRRRLPLANMSYYVSPQAVDAVHRGLGLPLPRTVPEQVRHNSMEDARELDEEVVEEADDDP

I would like to replace index position 383 (Q) with nothing after it, so the desired outcome would be:

MALYYDHQIEAPDAAGSPSFISWHPVHPFLAVAYISTTSTGSVDIYLEQGECVPDTHVERPFRVASLCWHPTRLVLAVGWETGEVTVFNKQDKEQHTMPLTHTADITVLRWSPSGNCLLSGDRLGVLLLWRLDQRGRVQGTPLLKHEYGKHLTHCIFRLPPPGEDLVQLAKAAVSGDEKALDMFNWKKSSSGSLLKMGSHEGLLFFVSLMDGTVHYVDEKGKTTQVVSADSTIQMLFYMEKREALVVVTENLRLSLYTVPPEGKAEEVMKVKLSGKTGRRADIALIEGSLLVMAVGEAALRFWDIERGENYILSPDEKFGFEKGENMNCVCYCKVKGLLAAGTDRGRVAMWRKVPDFLGSPGAEGKDRWALQTPTELQGNITQ

I have tried:

sed 's/"Q"//383' text.file
sed 's/Q//383' text.file

But that does not do anything.

In the long term I need to do with with a few other positions so a method that is flexible would be much appreciated.

All the best

A simple substr in awk would work here, like: awk '{print substr($0,1,383)}' Input_file. — RavinderSingh13
– RavinderSingh13, Commented Oct 25, 2021 at 12:54
sed 's/Q//383' text.file prompts sed to remove 383th occurence of Q, as there is only 69 Qs no action is taken — Daweo
– Daweo, Commented Oct 25, 2021 at 14:02
Please specify whether the file has any kind of line delimiter, or is just one long string of capital letters. — agc
– agc, Commented Oct 27, 2021 at 1:34

potong · Accepted Answer · 2021-10-25 13:05:22Z

4

This might work for you (GNU sed):

sed -zEi 's/(.{383}).*/\1/' file

Store the first 383 characters as a back reference and remove the rest.

N.B. the -z option slurps the entire file into memory.

answered Oct 25, 2021 at 13:05

potong

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Paolo · Accepted Answer · 2021-10-25 13:14:11Z

4

You could do this with cut:

cut -c 1-383 < text.file

edited Oct 25, 2021 at 13:14

answered Oct 25, 2021 at 12:57

Paolo

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dawg · Accepted Answer · 2021-10-25 13:10:12Z

3

GNU awk:

gawk '{print gensub(/(.{383}).*/,"\\1","1")}' file

answered Oct 25, 2021 at 13:10

dawg

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Andreas Louv · Accepted Answer · 2021-10-25 13:08:02Z

2

Just to throw it into the pool, head can be used to cut off after n lines, but also after c bytes:

$ head -c 383 text.file

answered Oct 25, 2021 at 13:08

Andreas Louv

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Renaud Pacalet · Accepted Answer · 2021-10-25 12:58:55Z

1

If you store your string in a bash variable you can use bash parameter expansion:

mystring=$(cat text.file)
echo "${mystring:0:383}"

answered Oct 25, 2021 at 12:58

Renaud Pacalet

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Darkman · Accepted Answer · 2021-10-25 16:43:26Z

1

Another option: dd

dd if=txt.file bs=383 count=1 status=none

answered Oct 25, 2021 at 16:43

Darkman

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agc · Accepted Answer · 2021-10-27 01:49:15Z

1

Using bash and printf:

 printf '%.383s\n' $(<text.file)

answered Oct 27, 2021 at 1:49

agc

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