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$ perl --version
This is perl, v5.10.1 (*) built for x86_64-linux-gnu-thread-multi
$ echo -e "foo\nbar" > baz.txt
$ perl -p -e 's/foo\nbar/FOO\nBAR/m' baz.txt
foo
bar
How can I get this replacement to work?
332
Solution. Use /m , /s , or both as pattern modifiers. /s lets . match newline (normally it doesn't). If the string had more than one line in it, then /foo.
Performing a regex search-and-replace is just as easy: $string =~ s/regex/replacement/g; I added a “g” after the last forward slash. The “g” stands for “global”, which tells Perl to replace all matches, and not just the first one.
And 0777 will force Perl to read the whole file in one shot because 0777 is not a legal character value. -- This option must be used in conjunction with either the -n or -p option. Using the -a option will automatically feed input lines to the split function. The results of the split are placed into the @F variable.
You can use the -0 switch to change the input separator:
perl -0777pe 's/foo\nbar/FOO\nBAR/' baz.txt
-0777 sets the separator to undef, -0 alone sets it to \0 which might work for text files not containing the null byte.
Note that /m is needless as the regex does not contain ^ nor $.
89
It has to do with the -p switch. It reads input one line at a time. So you cannot run a regexp against a newline between two lines because it will never match. One thing you can do is to read all input modifying variable $/ and apply the regexp to it. One way:
perl -e 'undef $/; $s = <>; $s =~ s/foo\nbar/FOO\nBAR/; print $s' baz.txt
It yields:
FOO
BAR
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