Gsub!("\n","\n")

Ruby
1

Hi all, I’m not sure why but I assumed gsub! would allow me to replace
\n with line feeds or \r for carriage returns.

How do I gsub! and replace everything with a nonvisible character like
newline? I was using this results.gsub!("\n","\n") but obviously that
does not work :frowning: also tried results.gsub!("\n",10.chr). No go.

Kinda of frustrating for something so simple. I guess I could always do
some recursion. Thanks.

2

On Jan 19, 2009, at 7:19 PM, Simon T. wrote:

–
Are you trying to turn this:

Hello,
World

Into something like:

Hello,\nWorld

If so, you need to change “\n” (1 character string) into “\\n” (3
character string, two escaped backslashs and the letter ‘n’). The
replacement string will undergo two different interpretations: as a
string literal “\\n” becomes \n which when interpreted as a
replacement for a regexp undergoes another round (so that things like
\1 and \2 can reference groups in the regexp) and becomes \n

Yes, this is tricky, but it’s because there are two levels of escaping
going on and both use the backslash.

-Rob

Rob B. http://agileconsultingllc.com
[email protected]

3

haha actually, the other way around :slight_smile: I have a string(I believe…I’m
using Hpricot to retreive web pages and it likes to add slashes to
everything). For example, I want to change “Hello, \nWorld” by changing
\n into a newline. So the output should be like:
Hello
World

I did try your suggestion, but I get “Hello\nWorld”. Will keep playing
with the slashes.

Rob B. wrote:

On Jan 19, 2009, at 7:19 PM, Simon T. wrote:

–
Are you trying to turn this:

Hello,
World

Into something like:

Hello,\nWorld

If so, you need to change “\n” (1 character string) into “\\n” (3
character string, two escaped backslashs and the letter ‘n’). The
replacement string will undergo two different interpretations: as a
string literal “\\n” becomes \n which when interpreted as a
replacement for a regexp undergoes another round (so that things like
\1 and \2 can reference groups in the regexp) and becomes \n

Yes, this is tricky, but it’s because there are two levels of escaping
going on and both use the backslash.

-Rob

Rob B. http://agileconsultingllc.com
[email protected]

4

Are you seeing something like:
irb> look = ‘here is a " and I'll put a ' here, too’
=> “here is a " and I’ll put a ’ here, too”
irb> puts look
here is a " and I’ll put a ’ here, too
=> nil

The rules for what needs to be escaped depend on the kind of quotes
used.

Are you seeing output that is shown in double quotes to indicate that
it is a string?

-Rob

On Jan 19, 2009, at 8:16 PM, Simon T. wrote:

I did try your suggestion, but I get “Hello\nWorld”. Will keep

World
\1 and \2 can reference groups in the regexp) and becomes \n
–
Posted via http://www.ruby-forum.com/.

Rob B. http://agileconsultingllc.com
[email protected]
+1 513-295-4739
Skype: rob.biedenharn

5

Simon T. wrote:
If you want to substitute
Hello\nWorld by
Hello
World
you should try to work with single quotes:
a = ‘Hello\nWorld’

Simon T. wrote:
=> “Hello\nWorld”
irb(main):002:0> puts a
Hello\nWorld
=> nil
irb(main):003:0> a.gsub!(’\n’,"\n")
=> “Hello\nWorld”
irb(main):004:0> puts a
Hello
World

6

Hi,

Am Dienstag, 20. Jan 2009, 09:19:02 +0900 schrieb Simon T.:

Hi all, I’m not sure why but I assumed gsub! would allow me to replace
\n with line feeds or \r for carriage returns.

str.gsub! “\n”, “\n”
str.gsub! “\r”, “\r”

This is a security risk:

eval %Q("#{str}")

Maybe this does:

str = “hello\nbye”
str.gsub! /\(\w)/ do |m| eval ‘"\’ + $1 + ‘"’ end

Okay, \ escaping is a weird matter.

You know that gsub! returns nil in case nothing was changed?

Bertram

7

Simon T. wrote:

I have a string(I believe…I’m
using Hpricot to retreive web pages and it likes to add slashes to
everything). For example, I want to change “Hello, \nWorld” by changing
\n into a newline.

Perhaps there’s a misunderstanding here. I doubt Hpricot adds anything.
If you see this “Hello, \nWorld” in ‘irb’ then that’s because ‘irb’
shows you the string in the way you’d write it in your source-code. The
two characters “\n” are actually a newline.

8

Ok, I just realized I’ve been using p to print everything out! “Puts”
works a whole lot better. Doh! Thanks for all the help. Sorry for
phrasing the question poorly :slight_smile:

9

On Jan 24, 2009, at 7:25 PM, Simon T. [email protected] wrote:

Ok, I just realized I’ve been using p to print everything out! “Puts”
works a whole lot better. Doh! Thanks for all the help. Sorry for
phrasing the question poorly :slight_smile:

–
Posted via http://www.ruby-forum.com/.

LOL!

10

Simon T. wrote:

I’m not sure why but I assumed gsub! would allow me to replace
\n with line feeds

“\n” is a line feed.

string = “hello\nworld”
=> “hello\nworld”

puts string
hello
world
=> nil

HTH,
Sebastian