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Bug #18957

closed

StringIO#printf doesn't ignore initial String value

Added by andrykonchin (Andrew Konchin) about 2 months ago. Updated about 2 months ago.

Status:
Rejected
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:109430]

Description

I've noticed that StringIO#printf diverges from IO#printf in the following way:

IO:

File.write("printf.txt", "1234567890")
f = File.open("printf.txt", "w+")
f.printf("%s", "abc")
f.rewind
f.gets
# => "abc"

StringIO:

io = StringIO.new("1234567890")
io.printf("%s", "abc")
io.rewind
io.gets
=> "abc4567890"

So File opened in a w mode "truncates" existing file content but StirngIO (by default) doesn't.

I would expect StringIO behaves in the same way.

Updated by mame (Yusuke Endoh) about 2 months ago

StringIO behaves like File.open with an r+ mode.

File.write("printf.txt", "1234567890")
f = File.open("printf.txt", "r+")
f.printf("%s", "abc")
f.rewind
p f.gets #=> "abc4567890"

Is there any reason for you to expect it to be the same as w+ mode instead of r+?

Updated by andrykonchin (Andrew Konchin) about 2 months ago

Good point. I overlooked the difference between r+ and w+. Thank you for clarification.

Actions #3

Updated by jeremyevans0 (Jeremy Evans) about 2 months ago

  • Status changed from Open to Rejected
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