Back Referencing in SED

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01-02-2009

sinpeak

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Back Referencing in SED

Hi,

I have tried all examples of back referencing from the web but all in vain.
It would be heavily helpful if someone explains me the use of back referencing and sub expression using an example of substitution.

Thanks

sinpeak

01-02-2009

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Hi,

Code:

sed 's/a\(..\)a/\1/' <<< "abba"

output:

Code:

bb

The backreference \1 saves the two characters betweens the as.
Everything between \(\) is saved and can be refereced with
\1 to \9 for each \(\).

HTH Chris

Christoph Spohr

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