Print int from signal handler using write or async-safe functions
async-safe, c, signals
Solution
If you really insist on doing the printing from a signal handler, you basically have 2 options:
Block the signal except in a dedicated thread you create for handling the signal. This special thread can simply perform `for (;;) pause();` and since `pause` is async-signal-safe, the signal handler is allowed to use any functions it wants; it's not restricted to only async-signal-safe functions. On the other hand, it does have to access shared resources in a thread-safe way, since you're now dealing with threads.
Write your own code for converting integers to decimal strings. It's just a simple loop of using `%10` and `/10` to peel off the last digit and storing them to a short array.
However, I would highly recommend getting this operation out of the signal handler, using the self-pipe trick or similar.
Problem
I want to print a number into log or to a terminal using `write` (or any async-safe function) inside a signal handler. I would prefer not to use buffered I/O. Is there an easy and recommended way to do that ? For example in place of `printf`, below I would prefer `write` (or any asyn safe function). ``` void signal_handler(int sig) { pid_t pid; int stat; int old_errno = errno; while((pid = waitpid(-1, &stat, WNOHANG)) > 0) printf("child %d terminated\n", pid); errno = old_errno; return; } ``` Printing strings is easy. In place of the `printf` above I can use (without printing `pid`): ``` write(STDOUT_FILENO, "child terminated", 16); ```