Re^2: Can't get \n or other character/translation escapes to interpolate if originally read from a data file

So, to be able to search for this 2-line string in a document that uses Unix-type line endings:

Reach Holly Smith for help by sending an email
To hollysmith@nosuchdomain.com.

.... the character-specific way to do it (rather than using \n) would have been to store the “old string”~“new string” line in a __DATA__ block, like this, using the Unix-type newline character (code point 10, or 0A in hexadecimal):

__DATA__
Reach Holly Smith for help by sending an email\x{0A}to hollysmith@nosuchdomain.com.~For more information, contact Holly Smith.

...where the preceding line is a single line even though it almost certainly will wrap on this web page; is that what you mean?

I think I’m coming to see the point of being able to use \n in a regular expression — it avoids the need to specify what the characters are that represent a new line in the operating system being used to write and read the file, and it’s a memorable way to avoid having to look up the code point for those characters. Plus a manual entry of a new line at the keyboard while creating a line-by-line data file would gunk up the use of

while ( <DATA> )

Comment on Re^2: Can't get \n or other character/translation escapes to interpolate if originally read from a data file

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Re^3: Can't get \n or other character/translation escapes to interpolate if originally read from a data file by AnomalousMonk (Archbishop) on Mar 16, 2021 at 21:58 UTC
Update: davebaker changed this post (without citation!) while I was composing this reply. ... a data block or file that contains “old string”~“new string” lines: `__DATA__` `... an email\x{0A}to ....~For more information, ....` (Is that what you mean?) No. (Well, at least that's not the point I would make. :) The point I would make is that the string you ~~get~~ \| read from a `__DATA__` or `__END__` block or from a regular file is essentially the same as a single-quoted string defined in a script, and such a string can be used directly as a regex search pattern: `Win8 Strawberry 5.8.9.5 (32) Tue 03/16/2021 17:26:59 C:\@Work\Perl\monks\davebaker >perl -Mstrict -Mwarnings my $s = 'foo bar'; print "A: >>$s<< \n"; my $search = 'foo\nbar'; # note single quotes! print "B: >>$search<< \n"; # \n is '\n' my $replace = "hoo-ray"; # can be single/double quotes $s =~ s/$search/$replace/; # no /g - one replacement only print "C: >>$s<< \n"; ^Z A: >>foo bar<< B: >>foo\nbar<< C: >>hoo-ray<<` [download] If the search string/pattern is held in a file, the process is similar, except you usually need to chomp the string before you use it: `Win8 Strawberry 5.8.9.5 (32) Tue 03/16/2021 17:28:26 C:\@Work\Perl\monks\davebaker >type search.dat foo\nbar >perl -Mstrict -Mwarnings my $s = 'foo bar'; print "A: >>$s<< \n"; open my $fh, '<', 'search.dat' or die "opening: $!"; chomp(my $search = <$fh>); print "B: >>$search<< \n"; # \n is essentially '\n' my $replace = "hoo-ray"; $s =~ s/$search/$replace/; print "C: >>$s<< \n"; ^Z A: >>foo bar<< B: >>foo\nbar<< C: >>hoo-ray<<` [download] I think that if you use `'\n'` (or the equivalent from a file) in a regex search pattern and if you use default I/O for reading all your files, then you will be able to do automatic text editing in an OS-agnostic way, at least across the Windows/nix iron curtain. The `'\n'` sequence in a regex* is the universal representation of a default newline. (In general, I think use of `qr//` is definitely best practice for defining search regexes in a script, not single- or double-quoted strings, but if you're reading from a file, you're kinda stuck with what you've got.) Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^3: Can't get \n or other character/translation escapes to interpolate if originally read from a data file by LanX (Saint) on Mar 16, 2021 at 13:03 UTC
I'm not sure I understand your question. If you want OS sensitive line breaks in `DATA` you'll need to translate them. I'd suggest using plain "enter" in the input and `$output = join "\n", <DATA>` In case of OS problems when reading DATA by line, just adjust `$/` before. (Never happened to me ) > Is that what you mean?* I suggested using HERE-docs instead of DATA. They are per default interpolated. Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery} update *) actually, this problem can't arise, because Perl reads DATA like it's own code, its the same filehandle. I.e. the script won't run if there where any problems with OS specific line-endings	[reply] [d/l] [select]

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