Perl command line one-liner to find regular expression matches that span multiple lines?

For example, I have a file foo.txt that contains

abc
bcc
ccc
baa

and I want to return the indexes of all instances of "c\nb" (in this case, the string is found at starting at the third and eleventh characters of the file). What's the simplest way t开发者_JS百科o accomplish this?

If you're sure the file is small enough to fit comfortably into memory, you can just slurp it into a variable and apply a regex to it:

$ perl -0777 -ne 'print $-[0], "\n" while /c\nb/g' foo.txt

Otherwise:

$ perl -ne 'print $n - 2, "\n" if /^b/ && $last =~ /c$/; $last = $_; $n += length' foo.txt

Note that these solutions depend on the input file containing only ASCII characters.

#!/usr/bin/perl

my $s = 'abc
bcc
ccc
baa';

while ($s =~ /c\nb/mg ) {
  print pos($s), "\n"
}

this will output 5, 13 (the pos function returns the index of the end of the match, but you should be able to compensate for that).

I'm sure there's a decent regex solution to this, but I'll fall back on the older index function:

$_ = q[abc
bcc
ccc
baa];

my $z; print $z++,"\n" while 0<=($z=index($_,"c\nb",$z));

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