WSTOPSIGstatus

WSTOPSIG status refers to the WSTOPSIG macro, a part of the POSIX wait family used in conjunction with wait or waitpid. Defined in the header <sys/wait.h>, WSTOPSIG(status) returns the signal number that caused a traced or child process to stop. The macro yields a meaningful value only when the status indicates that the child has stopped.

In practice, a programmer first tests the status with WIFSTOPPED(status). If true, WSTOPSIG(status) provides the specific signal that stopped the child, typically a SIGSTOP, SIGTSTP, SIGTTIN, or other stop signal. This information is useful in implementing job control, shells, debuggers, or other process-management tools that need to react to a stopped process.

Usage notes:

- Include the header <sys/wait.h>.

- Use WIFSTOPPED(status) to confirm the child is stopped before calling WSTOPSIG(status).

- The value returned by WSTOPSIG(status) is an int corresponding to a standard SIG* signal number as defined by signal.h.

Example (conceptual):

- pid, status;

- waitpid(-1, &status, WUNTRACED);

- if (WIFSTOPPED(status)) { int sig = WSTOPSIG(status); /* handle stop by signal sig */ }

Related macros include WIFEXITED, WEXITSTATUS, WIFSIGNALED, WTERMSIG, and WIFCONTINUED/WCONTINUED, which cover other termination and continuation scenarios. WSTOPSIG is specifically about the signal responsible for stopping a process, not for its normal exit or termination by a signal.