Using DTruss to Debug Slow Startup of Midnight Commander (MC) on MacOS

Midnight Commander (MC) is a powerful and fast file manager that works well over SSH. However, some users have reported experiencing slow startup times when using MC on Mac OS X. In this article, we'll explore how to use the DTruss tool to debug the problem and improve startup performance.

The Challenge

One of the challenges in debugging MC's slow startup is that it's difficult to attach a debugger to the process without interfering with its operation. The trick is to use DTruss to attach to another program, follow child processes as they are started, and have this other program wait until DTruss has attached before starting MC.

The First Problem: Attaching to the Process

One of the problems when using DTruss to debug MC's slow startup is that it requires root privilege to run. This means that by the time DTruss is attached, MC would have finished starting up. To solve this problem, we can run DTruss in a different terminal as a normal user and attach it to the MC process.

The Second Problem: Obscuring Output

Another challenge when using DTruss with MC is that the output of DTruss will be obscured by the ncurses interface of MC. This makes it difficult to see the output of the debug information.

Finding the Solution

To find the solution, we can use DTruss to print out details of the system calls a program makes. By using DTruss in conjunction with another program, we can follow child processes and attach to them before they start up.

The Final Solution

One possible solution is to run DTruss in a different terminal as root, and then attach it to the MC process when it starts up. This allows us to see the debug information without interfering with MC's operation. By using this approach, we can identify the system calls that are causing MC to take longer than usual to start up.

In conclusion, DTruss is a powerful tool for debugging all sorts of problems on Mac OS X. While it can be tricky to use with interactive text-mode programs like MC, it's still possible to find solutions using this approach. By attaching DTruss to another program and following child processes, we can identify the system calls that are causing slow startup times and improve performance.

Midnight commander macos