Hello,
Consider the case:
You have 200 lines of mapping to replace, in a csv format, e.g.
apple,orange
boy,girl
...
You have a 500MB file, you want to replace all 200 lines of mapping,
what would be the most efficient way to do it?
Thanks.
If you want to replace the whole line or know the column where you
need to replace it and the line has clear separators you may be be a
lot faster if you do it using awk:
cat csv|awk -F"," "$2~/apple/ {$2="orange"; print $1,$2} " ...
otherwise I don't see a reason not to use the most obvious way:
starting from line 1 and running until the end ... especially if dont
know *where* the 200 lines are ...
#! /usr/bin/perl -w
%replace=('apple'=>'orange','boy'=>'girl');
$r="(".join ("|", keys %replace ).")";$r=qr($r);
while (<>) {
s/$r/$replace{$1}/g;
print;
}
[08:07:43] cvh@lenny:~$ echo "a boy named sue sings a song for apple
jack" | perl repl.pl
a girl named sue sings a song for orange jack
[08:07:45] cvh@lenny:~$ echo "a boy named sue sings a song for apple
jack" > test.txt
[08:07:59] cvh@lenny:~$ perl repl.pl test.txt
a girl named sue sings a song for orange jack
[08:08:11] cvh@lenny:~$ perl repl.pl test.txt >test_replace.txt
[08:08:24] cvh@lenny:~$ cat test_replace.txt
a girl named sue sings a song for orange jack
[08:08:40] cvh@lenny:~$
