How to read a file in Crystal?

Question

I recently picked up on Crystal after being a Rubyist for a while, and I can't seem to find anything about the File class. I want to open and read a file, but it gives me an error.

file = File.open("ditto.txt")
file = file.read

tequila@tequila-pc:~/code$ crystal fileopen.cr
Error in fileopen.cr:2: wrong number of arguments for 'File#read' (given 0, expected 1)
Overloads are:
 - IO::Buffered#read(slice : Bytes)
 - IO#read(slice : Bytes)

file = file.read
            ^~~~

Mavismavra

Note that the error message also says IO#read(slice : Bytes) – File inherits the read method from IO. According to the docs for IO#read it expects an argument. You might want to try the File.read class method instead. – Paton

Answer 1

You're probably looking for IO#gets_to_end which reads the entire file as a String. But you might as well use File.read

file_content = File.read("ditto.txt")

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IO#read is a different, more low-level method which allows to read pieces of an IO into a byte slice.

Bunny