What are the Ruby File.open modes and options?

194
votes

Ruby's File.open takes modes and options as arguments. Where do I find a complete list of modes and options?

2
rubyfile-io
ruby-doc.org/core-2.0.0/IO.html#method-c-new-label-IO+Open+Mode - The link to this page is in Daniels answer below but you have to scroll the page to get to it. Here's the direct link to the relevant part of the docs. – newUserNameHere

2 Answers

402
votes

In Ruby IO module documentation, I suppose.

Mode |  Meaning
-----+--------------------------------------------------------
"r"  |  Read-only, starts at beginning of file  (default mode).
-----+--------------------------------------------------------
"r+" |  Read-write, starts at beginning of file.
-----+--------------------------------------------------------
"w"  |  Write-only, truncates existing file
     |  to zero length or creates a new file for writing.
-----+--------------------------------------------------------
"w+" |  Read-write, truncates existing file to zero length
     |  or creates a new file for reading and writing.
-----+--------------------------------------------------------
"a"  |  Write-only, starts at end of file if file exists,
     |  otherwise creates a new file for writing.
-----+--------------------------------------------------------
"a+" |  Read-write, starts at end of file if file exists,
     |  otherwise creates a new file for reading and
     |  writing.
-----+--------------------------------------------------------
"b"  |  Binary file mode (may appear with
     |  any of the key letters listed above).
     |  Suppresses EOL <-> CRLF conversion on Windows. And
     |  sets external encoding to ASCII-8BIT unless explicitly
     |  specified.
-----+--------------------------------------------------------
"t"  |  Text file mode (may appear with
     |  any of the key letters listed above except "b").
6
votes

opt is new for ruby 1.9. The various options are documented in IO.new : www.ruby-doc.org/core/IO.html