What's a reasonable way to read an entire text file as a single string?

Question

I am sure this is an easy one; I just couldn't find the answer immediately from Google.

I know I could do this (right?):

text = ""
File.open(path).each_line do |line|
    text += line
end

# Do something with text

But that seems a bit excessive, doesn't it? Or is that the way one would do it in Ruby?

Caveat: Reading the file into memory, AKA slurping, has scalability issues. Ruby, along with Perl and other languages, can read a file line by line almost as fast as it can reading then splitting and looping through it. — the Tin Man, Nov 19 '11 at 11:53
@the Tin Man: That's good advice, and I thank you for it. This question was asked a while ago, so I could be remembering it incorrectly; but I believe my intention at the time was to do some multi-line regex matching on the text of the file, so I did need the whole thing in memory (i.e., I wasn't just planning on reading it line-by-line). — Dan Tao, Nov 20 '11 at 17:41

Thiago Silveira · Answer 1 · 2013-07-05T20:12:40.870

197

IO.read() is what you're looking for.
File is a subclass of IO, so you may as well just use:

text = File.read(path)

Can't get more intuitive than that.

edited Jul 05 '13 at 20:12

answered Jun 24 '11 at 18:48

Thiago Silveira

1

Like my question for s.m., does IO, or File read the whole file into memory, or does it use a file pointer with SEEK to keep track of that instead of loading a big file into memory? – FilBot3 May 23 '15 at 21:23
3

@Pred it loads it into a string and therefore into memory. – Travis Reeder Jul 15 '16 at 15:32

s.m. · Accepted Answer · 2011-06-24T18:48:50.673

45

What about IO.read()?

Edit: IO.read(), as an added bonus, closes the file for you.

edited Jun 24 '11 at 18:48

answered Jun 24 '11 at 18:41

s.m.

1

Does this put the entire file into memory, or does it keep a file pointer so it doesn't use all of your RAM reading a huge file? – FilBot3 May 23 '15 at 21:22

score 0 · Answer 3 · answered Oct 12 '21 at 09:20

First result I found when searching.

I wanted to change the mode, which doesn't seem possible with IO.read, unless I'm wrong?

Anyway, you can do this:

data = File.open(path,'rb',&:read)

It's also good for when you want to use any of the other options:

3 Answers3