How can I pipe stdin from a file to the executable in Xcode 4+?

Question

I have an mpi program and managed to compile and link it via Xcode 4. Now I want to debug it using Xcode 4.

How can I pipe the standard input to the program from a file?

In terminal I would type

mpirun -np 2 program < input.txt 

I am able to run the program defining a custom executable (mpirun) in the "Info" panel of the Scheme editor, I also know that I can pass arguments in the "Arguments" panel. But Xcode 4 does not seem to accept "< input.txt" as an argument, even if I check "Use custom working directory" + add the correct directory of the input script in the "Options" panel.

This article Says it is possible to use "< input.txt" as an argument, but I guess that worked in Xcode 2 or Xcode 3, but it does not seem to work in Xcode 4 anymore.

Answer 1

In Xcode 4.5.1:

1. Open the scheme editor (Product menu -> Edit Scheme...)
2. Select the Run Debug scheme
3. In the 'Info' tab panel, change the 'Launch' radio button selection from 'Automatically' to 'Wait for MyApp.app to launch'
4. Close the scheme editor
5. Press the Run button to build and run your target. (Xcode's status window in the toolbar will show 'Waiting for MyApp to launch')
6. Launch Terminal and cd to your built application's folder. (It will be something like /Users/user/Library/Developer/Xcode/DerivedData/MyApp-dmzfrqdevydjuqbexdivolfeujsj/Build/Products/Debug / )

7. Launch your app piping in whatever you want into standard input:

   echo mydata | ./MyApp.app/Contents/MacOs/MyApp 

8. Switch back to Xcode and the debugger will have detected your application's launch and attached to it.

Answer 2

Not wanting to awaken zombies, but this is still the top search result for the question.

I've managed to get this working in XCode 9.2 - but it should be backwards compatible. It uses a subshell and sleep in a pre-action script. This will pipe from a file and stick cout to a file, and supports breakpoints.

(1) Add the following preaction.sh script into your project.

#!/bin/sh exec > ${PROJECT_DIR}/tests/result.log 2>&1 ( sleep 1 ${TARGET_BUILD_DIR}/${EXECUTABLE_NAME} < ${PROJECT_DIR}/tests/file )& 

(2) Then add it to your pre-actions on the Run menu.

(3) Ensure your run Waits for executable to be launched.

(4) Turn off code signing for your target!

Otherwise you will get an error "Message from debugger: unable to attach"

(5) Set breakpoints and run from Xcode as normal

That's all there is to it. The entire trick rests on getting the pre-action script to spawn off a sub-shell that itself delays the process until the run action is launched.