Perl replace match+nextline+match

Question

I have lines in file:

Desktop DELL firewall UP CPU 20core configured 
Desktop HP firewall DOWN CPU 18core unconfigured

I want to first match UP and then if next line match DOWN replace these two lines with some string

I tried

perl -p -e 's?.*firewall.*UP.*\n.*firewall.*DOWN.*?STRG?' file

but it doesnt work

Possible duplicate: [How to replace multiple any-character (including newline) in Perl RegEx?](https://stackoverflow.com/q/36533282/2173773) — Håkon Hægland, Aug 12 '17 at 13:51

score 2 · Answer 1 · answered Aug 11 '17 at 23:59

2

/\n.*f/ can't possibly match since you are reading newline-terminated lines one at a time.

A convenient trick is to use -0777 to load the entire file into memory at once.

perl -0777pe's/^.*firewall.*UP.*\n.*firewall.*DOWN.*/STRG/m' file

answered Aug 11 '17 at 23:59

ikegami

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Casimir et Hippolyte · Answer 2 · 2017-08-12T12:02:09.463

1

With sed:

sed '/firewall.*UP/{N;/firewall[^\n]*DOWN/s/.*/somestr/}' file

details:

/firewall.*UP/ {      # condition
    N;                # append the next line to the pattern space
    /firewall[^\n]*DOWN/  # condition
        s/.*/somestr/ # then: replace all with somestr
}

edited Aug 12 '17 at 12:02

answered Aug 11 '17 at 22:36

Casimir et Hippolyte

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Might this create a false positive if `DOWN` was in the same line as `UP`? – potong Aug 12 '17 at 11:22
@potong: clearly yes, but I doubt this can happen. However I will replace the second `.*` with `[^\n]*` to be sure that *firewall* and *DOWN* are on the same line (the second one). – Casimir et Hippolyte Aug 12 '17 at 12:01

Perl replace match+nextline+match

2 Answers2