1.2 KiB
Read The First Line From A File
If I wanted to read the first line from a file with Ruby, I'd probably read the whole thing in, split it by newlines, and grab the first.
File.read('README.md').split(/\n/).first
This is inefficient in that it reads in the entire file. For small files this won't matter, but for larger files it could become a bottleneck.
There is a method of doing this that is just as concise and streams the first
part of the file rather than reading it in its entirety. The File.open method
takes a block. This means you can pass a symbol-to-proc to it as the block
argument.
> File.open('README.md', &:readline).strip
=> "# TIL"
> File.open('README.md', &:gets).strip
=> "# TIL"
Both #readline and #gets will grab the first line including the newline
character (hence the #strip). The only difference is that #readline will
raise an exception if the file is empty.
These methods both come from the IO module and stream the file rather than
slurping the whole thing
in.