During the execution of a C compiled program in a terminal, isatty(fileno(stderr)) as well as isatty(0) returns 0 in my code when I use the mpirun or mpiexec commands.

Why ? and How do I know if stdout is a terminal or redirected while using MPI ?

I'm actually printing colored stuff, but this makes the output parsing harder.

Thanks in advance.

CodePudding user response：

mpirun/mpiexec starts all processes with stdout/stderr connected to a pipe or socket that leads back to the mpirun process. The mpirun process collects everything from all of these pipes/sockets and copies it to its stdout.

So only mpirun itself still has stdout/stderr still connected to a terminal. Any other process will see its stdout/stderr connected to a non-terminal.

Your best bet is to use an argument or environment variable to control whether the output is colored or not.