Re: codeperl -pe 's/\n/

I'm sure the author will be able to explain it better, but here it goes:

The -p option creates an implicit
```
while(<>) { ... ; print }
[download]
```
loop around your code (which takes the place of the "...").
The /e modifier causes the replacement part to be evaluated as a perl expression, so the
```
" " . <>
[download]
```
is evaluated as "a space concatenated with the next line read from the input".

This makes more sense with an example. Let's say you have the file:

one
two
three
four
[download]

And run it through the code above. Here's what happens:

The "while(<>)" reads "one\n"
The s substitutes the "\n" in "one\n" with a space followed by the next line in the file ("two\n"), so $_ now contains "one two\n".
The implicit "print" (from the -p option) prints $_.
Repeat.

--ZZamboni

Comment on Re: codeperl -pe 's/\n/ Select or Download Code

Replies are listed 'Best First'.
RE: Re: codeperl -pe 's/\n/ by nuance (Hermit) on May 26, 2000 at 18:55 UTC
while I have no doubt that this is basicaly correct, I'm not convinced that it's 100% My understanding of the situation is that the regular expression operator iterates over the entire string before it moves on to the "implicit" print. This makes the order The "while(<>)" reads "one\n" The s substitutes the "\n" in "one\n" with a space followed by the next line in the file ("two\n"), so $_ now contains "one two\n". Substitution operator now carries on examining $_, finds \n at the end "one two\n" etc. The implicit "print" (from the -p option) prints $_. If it did the print as step three, surely you would end up with one two three four Update nuance hangs his head in shame :-( I really will have to learn to read posts properly, of course the original node mentions joining pairs of lines. Doh! As you can all see, my understanding was wrong. *Nuance* Baldrick, you wouldn't see a subtle plan if it painted itself purple and danced naked on top of a harpsichord, singing "Subtle plans are here again!"	[reply]
RE: RE: Re: codeperl -pe 's/\n/ by ZZamboni (Curate) on May 26, 2000 at 19:59 UTC
The purpose of the snippet is precisely to join the lines of the file two at a time. So yes, the output you give is the one you get, but that is the intended effect. The -p adds an implicit print at each iteration of the implicit loop.	[reply]
A reply falls below the community's threshold of quality. You may see it by logging in.