Problem with Ruby script output being stored into a file

Question

I have a Ruby script that outputs a heap of text. As an example:

puts "line 1"
puts "line 2"
puts "line 3"
# etc... (obviously, this isn't how my script works..)

There's not a lot of data - perhaps about 8kb of character data in total.

When I run the script on the command line, it works as expected:

$ ./my-script.rb

line 1
line 2
line 3

But, when I push it into a file, the output is truncated at exactly 4096 bytes:

$ ./my-script.rb > output.txt

What would cause it to stop at 4kb?

Update: I just rewrote the script to output directly to a file, rather than print to the screen and capture the output, and the problem is still happening!

$output = File.new("file.txt")
$output << "line 1"  #etc..

Answer 1

Does your program terminates correctly? 4kB can be the OS internal buffer size for I/O, and the following data, present in the next buffer (up to 8kB which is the total size of your data) is lost when your program terminates abruptly or does not terminate at all.