What does Wtermsig return?
If the WIFSIGNALED macro indicates that the child process exited because it raised a signal, the WTERMSIG macro returns the numeric value of the signal that was raised by the child process.
What is the return value of Waitpid?
RETURN VALUES If waitpid() returns because the status of a child process is available, it returns a value equal to the process ID of the child process for which status is reported. If waitpid() returns due to the delivery of a signal to the calling process, -1 is returned and errno is set to EINTR.
What does Wtermsig do?
WTERMSIG–Determine which signal caused the child process to exit. This macro queries the termination status of a child process to determine which signal caused the child process to exit. Status is provided by the wait and waitpid functions.
What is Wifexited return?
WIFEXITED and WEXITSTATUS are two of the options which can be used to know the exit status of the child. WIFEXITED(status) : returns true if the child terminated normally. WEXITSTATUS(status) : returns the exit status of the child. This macro should be employed only if WIFEXITED returned true.
What is difference between wait and Waitpid?
wait(): on success, returns the process ID of the terminated child; on failure, -1 is returned. waitpid(): on success, returns the process ID of the child whose state has changed; if WNOHANG was specified and one or more child(ren) specified by pid exist, but have not yet changed state, then 0 is returned.
What does Waitpid return Wnohang?
Returned value If successful, waitpid() returns a value of the process (usually a child) whose status information has been obtained. If WNOHANG was given, and if there is at least one process (usually a child) whose status information is not available, waitpid() returns 0.
What is pid_t pid?
The pid_t data type is a signed integer type which is capable of representing a process ID. In the GNU C Library, this is an int . Function: pid_t getpid (void) Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts. The getpid function returns the process ID of the current process.
Why is Waitpid useful?
It’s used generally to wait until a specific process finishes (or otherwise changes state if you’re using special flags), based on its process ID (otherwise known as a pid ). It can also be used to wait for any of a group of child processes, either one from a specific process group or any child of the current process.
What is SIGCHLD signal?
The SIGCHLD signal is the only signal that the z/TPF system sends to a process. When a child process created by the tpf_fork function ends, the z/TPF system: Sends a SIGCHLD signal to the parent process to indicate that the child process has ended.
What is wait (& status?
The wait() system call suspends execution of the current process until one of its children terminates. The call wait(&status) is equivalent to: waitpid(-1, &status, 0); The waitpid() system call suspends execution of the current process until a child specified by pid argument has changed state.