[SR-4029] Cannot get input in a subprocess started by a Swift program

[swift-ci]

Previous ID	SR-4029
Radar	None
Original Reporter	axl411 (JIRA User)
Type	Bug

Environment

Apple Swift version 3.0.2 (swiftlang-800.0.63 clang-800.0.42.1) Target: x86_64-apple-macosx10.9

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Foundation | |Labels | Bug | |Assignee | None | |Priority | Medium | md5: fbf53e7562d6b5e0dba637f3057d795d

Issue Description:

In a Swift program, I started a subprocess to run a Ruby script, in the script I expect to get some input.

It works as expected in Xcode, but does not work if I run it in terminal.

This is a demo demonstrating this: https://github.com/axl411/swift-get-input-problem

[belkadan]

I wonder if it's specifically related to using the interpreter. (That is, does running the Xcode-built binary in the Terminal work even though running the script directly doesn't?)

[swift-ci]

Comment by Chao Gu (JIRA)

Just did some tweak to the demo, confirmed that it is not related to the interpreter (running the Xcode-built binary in terminal does not work either).

Here is what I did:

• In `main.swift`, I changed the path to `subprocess.rb` an absolute path in my computer so the program can always find `subprocess.rb`

• I archived the program in Xcode, then exported it.

• I run the exported binary in terminal, it prompted me to "input something", then the same problem, my input wasn't accepted after I pressed `⏎`

[belkadan]

Interesting. It looks like something is doing an extra level of buffering in Terminal that isn't happening in Xcode. I think I'll have to turn it over to the Foundation folks to figure out the difference.

(My contribution: echo hi | ./main worked fine, as did echo hi | xcrun swift ./main.swift.)