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34 lines
1.2 KiB
Markdown
34 lines
1.2 KiB
Markdown
# Read The First Line From A File
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If I wanted to read the first line from a file with Ruby, I'd probably read the
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whole thing in, split it by newlines, and grab the first.
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```ruby
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File.read('README.md').split(/\n/).first
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```
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This is inefficient in that it reads in the entire file. For small files this
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won't matter, but for larger files it could become a bottleneck.
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There is a method of doing this that is just as concise and streams the first
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part of the file rather than reading it in its entirety. The `File.open` method
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takes a block. This means you can pass a symbol-to-proc to it as the block
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argument.
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```ruby
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> File.open('README.md', &:readline).strip
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=> "# TIL"
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> File.open('README.md', &:gets).strip
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=> "# TIL"
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```
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Both `#readline` and `#gets` will grab the first line including the newline
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character (hence the `#strip`). The only difference is that `#readline` will
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raise an exception if the file is empty.
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These methods both come from the `IO` module and [stream the file rather than
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slurping the whole thing
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in](https://blog.appsignal.com/2018/07/10/ruby-magic-slurping-and-streaming-files.html).
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[source](https://stackoverflow.com/questions/1490138/reading-the-first-line-of-a-file-in-ruby)
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