Unix Shell Script to extract the number from the String

Question

How to extract the bold number from the string below using unix shell script?

17: H.0(-2073):File ID (40008)in xyz file not equal to the file ID(**40004**)in file header.

Thanks :)

Sergey · Accepted Answer · 2015-04-10 07:54:11Z

3

echo '17: H.0(-2073):File ID (40008)in xyz file not equal to the file ID(40004)in file header.' | sed -e 's/.*(\([0-9]*\)).*/\1/'

The second part of this line runs sed with command s (substitution). Part between first two slashes (/) is regular expression which matches the following:

Everything (.*) in greedy manner, i.e. until the last occurrence of any number of digits in brackets ( ([0-9]*) ) and then everything again (.*) until the end of line. Expression between \( and \) (i.e. 40004 in this case) is memorized to be used in the second part of s command.

The part between the second / and third / is what we want to place instead of the line matched with regular expression. Here it is \1, meaning reference to the substring between 1st occurrence of \( and \) which is 40004 in our case.

So the part after | replaces the whole input string with string 40004 extracted from it. Regular expressions are powerful but often write-only technique, so I hope this explanation will bring a bit more clarity.

edited Apr 10, 2015 at 7:54

answered Apr 9, 2015 at 16:32

Sergey

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2 Comments

K K Over a year ago

could you please explain me the code ""sed -e 's/.*(([0-9]*)).*/\1/' "" How is it able to cut only Bold number?

Sergey Over a year ago

@KK Added some explanation.

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