search and replace string from a script

[Randal L. Schwartz]

In article <1991Apr23.180034.7349 at progress.com>, root at progress (Root of all Evil) writes:
| Is there any way within ex (or some other text processing utility) to
| access the nth occurrence of a pattern?  What I'd like to do is search
| a file for the nth occurrence of a pattern and then change that pattern
| but no others.  I've tried using ex:
| 
| ex -s FILE << QUIT
| /STRING1/n s/STRING1/STRING2/
| wq!
| QUIT
| 
| but this only places me n lines after the first occurrence of STRING1.
| Any ideas?  I'd like to avoid writing to a temporary file.

perl -pe '/STRING1/ && (++$n == 20) && s/STRING1/STRING2/' <in >out

OK, so the syntax is cryptic; do it C-like if you want:

perl -pe 'if (/STRING1/ && (++$n == 20)) { s/STRING1/STRING2/; }' <in >out

or even (more verbosely):

perl -pe 'if (/STRING1/) { s/STRING1/STRING2/ if ++$n == 20; }' <in >out

(well, maybe not more verbosely, then... :-)  Or even:

perl -pe 's/STRING1/STRING2/ if /STRING1/ && (++$n == 20);' <in >out

All of these presume "20" is your magic occurance.  Season to taste.

print "Just another Perl hacker," # Perl is available from all GNU sites...
-- 
/=Randal L. Schwartz, Stonehenge Consulting Services (503)777-0095 ==========\
| on contract to Intel's iWarp project, Beaverton, Oregon, USA, Sol III      |
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