Why are the three dots written to a new line?

Question

puts "Hello! Reading temperature value from data file..."
num = File.read("temp.dat")
puts "The number is #{num}..."
celsius = num.to_i
fahrenheit = (celsius.to_i * 9 / 5) + 32
puts "The Fahrenheit value is: #{ fahrenheit }."

In the third line, the ... after the #{num} block are printed in a new line. I was under the impression that using that block was passing parameter to the display allowing easier formatting.

Why are the dots going to a new line?

Because the file `temp.dat` contains NewLine character at the end? — manji, May 10 '11 at 15:41
If you're new to debugging Ruby, you may want to look at http://stackoverflow.com/questions/3955688/how-do-i-debug-ruby-scripts — Andrew Grimm, May 10 '11 at 23:19

score 5 · Accepted Answer · answered May 10 '11 at 15:42

When you read in a file, you get the newlines, too. Maybe what you're looking for is this:

celsius = File.readlines("temp.dat").first.to_i
puts "The number is #{celsius}..."

If you have a look at what you're reading it might make sense:

puts num.inspect
# => "20\n"

score 3 · Answer 2 · answered May 10 '11 at 15:42

3

Presumably temp.dat ends with a newline character, num contains a newline character. To remove the newline character, you can use the String#chomp method, which removes any newline character at the end of a string.

answered May 10 '11 at 15:42

sepp2k

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score 2 · Answer 3 · answered May 10 '11 at 15:44

2

My guess is that the newline is coming in from the file

If that is the case then

puts "The number is #{num.strip}..."

should fix it.

answered May 10 '11 at 15:44

seph

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the Tin Man · Answer 4 · 2015-11-09T17:26:54.050

Since you're trying to read an integer, the simplest way I know to read a single number from a file is:

File.read('temp.dat').to_i
# => 42

to_i will parse until the first non-digit which would be the "\n". At that point it'll stop reading and will return only the value, converted to an integer.

Doing that lets you clean your code and reduce it to:

puts "Hello! Reading temperature value from data file..."
celsius = File.read("temp.dat").to_i
puts "The number is #{ celsius }..."
fahrenheit = (celsius * 9 / 5) + 32
puts "The Fahrenheit value is: #{ fahrenheit }."

This is NOT how to read a file in general, it's just an answer to this particular question.

score 0 · Answer 5 · answered May 10 '11 at 15:49

When you read the file, you are also reading the carriage return/newline in the file. Use String#chomp to strip off this extra unwanted whitespace:

num = File.read("temp.dat").chomp
puts "The number is #{num}..."

See http://ruby-doc.org/core/classes/String.html#M001188 for more information.

Why are the three dots written to a new line?

5 Answers5