This is what I want to do, but with a one-liner:
lines = Array.new
File.open('test.txt').each { |line| lines << line }
Possible?
2 Answers
Do as below :
File.readlines('test.txt')
Read documentation :
arup@linux-wzza:~> ri IO::readlines
= IO::readlines
(from ruby site)
------------------------------------------------------------------------------
IO.readlines(name, sep=$/ [, open_args]) -> array
IO.readlines(name, limit [, open_args]) -> array
IO.readlines(name, sep, limit [, open_args]) -> array
------------------------------------------------------------------------------
Reads the entire file specified by name as individual lines, and
returns those lines in an array. Lines are separated by sep.
a = IO.readlines("testfile")
a[0] #=> "This is line one\n"
If the last argument is a hash, it's the keyword argument to open. See IO.read
for detail.
Example
arup@linux-wzza:~/Ruby> cat out.txt
name,age,location
Ram,12, UK
Jadu,11, USA
arup@linux-wzza:~/Ruby> ruby -e "p File::readlines('./out.txt')"
["name,age,location\n", "Ram,12, UK\n", "Jadu,11, USA\n"]
arup@linux-wzza:~/Ruby>
4 Comments
sandre89
How can't you love Ruby :)
Arup Rakshit
@sandre89 what do you mean? :)
sandre89
I meant that this is just one more example of such a brilliant and well designed language. You want to "read lines" from a "file" into an array, and Ruby's answer is
File.readlines(filename). :)
NYCdotNet
if your input file has a BOM you may have to specify the encoding such as
File.readlines(filename, encoding: 'bom|utf-8')I use the same File.readlines methods as explained in the accepted answer.
However when I read in strings from a text file, I typically want to get rid of the newline characters at the end of each line.
Therefore I use this:
File.readlines('adopters.txt').map(&:chomp)
IO::foreachdoes file processing line by line. But when someone is trying to get the lines in an array,#readlinesvery good way to go, rather thanar = []; File.foreach('test.txt') { |line| ar << line }. I didn't check, but I am sure, inClevel,readlines()probably does something like that internally already.As opposed to slurping up the whole file at once and then breaking it down into lines.eachis safe because it's the instance version offoreach. I have read the C source, andreadlinesdoesn't scale because it aggregates an entire file into memory. That's a bad practice, even today when machines have more memory and are faster, because files are bigger too. An unexpectedly big file, bigger than Ruby can handle, will take a machine to a crawl. That's unnecessary, and unacceptable in production environments.