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Accepted
Jeus Jimenez
Asked: 2022-10-21 08:23:52 +0800 CST 2022-10-21 08:23:52 +0800 CST

Search inside a file using grep

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In a .txt there are several DNIs, what I want to do is use the grep filter command to get the DNIs that have 9 numbers and 1 letter. I've tried this command but it doesn't work:

INSIDE THE FILE:

123456789A

31232g

42344324f

324f

4554345345345g

234452l

INSTRUCTION I HAVE USED:

cat nif.txt|grep -E "[[:digit:]]{9}[[:alpha:]]{1}"

123456789A

4554345345345g

I get the wrong ID and that's what I don't want it to do. Thanks in advance

linux

1 Answers

  1. Best Answer

    I suppose that if you count from the beginning those 9 characters plus the letter and also specify that later there should not be more characters, you will get it.

    To do this, use the symbol ^that indicates that the match to be searched for should start the line, and at the end you put a symbol $that indicates that after the pattern to be searched for there should be nothing else (indicates the end of the line):

    cat nif.txt|grep -E "^[[:digit:]]{9}[[:alpha:]]{1}$"

    because otherwise, as you had it, it didn't matter if more characters came out before finding it or after (for example, this was also found: 423443246fXXX `.

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