End of Life Ruby 3.0 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →
IO#gets
static VALUE
rb_io_gets_m(int argc, VALUE *argv, VALUE io)
{
VALUE str;
str = rb_io_getline(argc, argv, io);
rb_lastline_set(str);
return str;
}
Reads the next “line” from the I/O stream; lines are separated by sep. A separator of nil reads the entire contents, and a zero-length separator reads the input a paragraph at a time (two successive newlines in the input separate paragraphs). The stream must be opened for reading or an IOError will be raised. The line read in will be returned and also assigned to $_. Returns nil if called at end of file. If the first argument is an integer, or optional second argument is given, the returning string would not be longer than the given value in bytes.
File.new("testfile").gets #=> "This is line one\n" $_ #=> "This is line one\n" File.new("testfile").gets(4)#=> "This"
If IO contains multibyte characters byte then gets(1) returns character entirely:
# Russian characters take 2 bytes File.write("testfile", "\u{442 435 441 442}") File.open("testfile") {|f|f.gets(1)} #=> "\u0442" File.open("testfile") {|f|f.gets(2)} #=> "\u0442" File.open("testfile") {|f|f.gets(3)} #=> "\u0442\u0435" File.open("testfile") {|f|f.gets(4)} #=> "\u0442\u0435"
Ruby version changes
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3.0
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IO#wait_readable,IO#wait_writable,IO#read,IO#writeand other related methods (e.g.IO#puts,IO#gets) may invoke the scheduler hook io_wait(io, events, timeout) in a non-blocking execution context. [Feature #16786]
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