perl regex works in script but not when executed on the command line

Question

I'm trying to manipulate multiline CoffeeScript comments in a file using perl. This is my regex:

^\t*###[\S\s]*?^\t*###

When I run this in a script where data is the file data, it does what I expect and replaces all multiline comments with "foo":

$data =~ s{^\t*###[\S\s]*?^\t*###}{"foo"}gme;

However, when I run this on the command line the file is unchanged:

perl -pi -e 's{^\t*###[\S\s]*?^\t*###}{"foo"}gme' file.coffee

I've used similar commands with different regular expressions and without the 'm' option and they all work. Is it the m option that's causing the issue? I'm sure its something simple.

I'm curious if the filesystem is taking the \t as a literal tab char instead of the actual regex tab? What happens if you try escaping the backslashes? — brandonscript
– brandonscript, Commented Dec 1, 2013 at 4:31
I ran perl -pi -e 's{^\\t*###[\S\s]*?^\\t*###}{"foo"}gme' file.coffee and still no joy. — Ryan Lynch
– Ryan Lynch, Commented Dec 1, 2013 at 4:37

hwnd · Accepted Answer · 2013-12-01 07:32:57Z

4

In the implicit loops set by -n and -p it can be useful to define the values of $/ and $\. Using the -0 option puts Perl in paragraph mode and the special value 0777 puts Perl into file slurp mode.

perl -0777 -i -pe 's{^\t*###[\S\s]*?^\t*###}{"foo"}gme' file.coffee

answered Dec 1, 2013 at 7:32

hwnd

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1 Comment

Ryan Lynch Over a year ago

Thanks for putting this up as an answer for anyone who stumbles across this question.

nobody · Accepted Answer · 2013-12-01 04:38:20Z

3

The perl documentation for the -n/-p option states:

assume "while (<>) { ... }" loop around program

This means that each time the -e expression is executed, $_ is one line of the input file. Your s/// expression is expecting to operate on the whole entire file at once, so it won't work in this mode.

answered Dec 1, 2013 at 4:38

nobody

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6 Comments

Ryan Lynch Over a year ago

Is there any way I can operate on the whole file at once from the command line?

nobody Over a year ago

Not in-place that I can find, but you could probably do something like: perl -e 'local $/; $data = <>; $data =~ s/find/replace/; print $data' < file > file.new && mv file.new file

hwnd Over a year ago

@RyanLynch You can slurp the file.

Ryan Lynch Over a year ago

Thanks @hwnd. I'll think about asking another question now that I know what the issue is.

hwnd Over a year ago

Try this perl -0777 -i -pe 's{^\t*###[\S\s]*?^\t*###}{"foo"}gme' file.coffee

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