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waitid(2) System Calls Manual waitid(2) NAME waitid - Wait for child process to change state SYNOPSIS #include <sys/wait.h> int waitid( idtype_t idtype, id_t id, siginfo_t *infop, int options); STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: waitid(): XPG4-UNIX Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. PARAMETERS Identifies the type of process to be affected. Used with the id para- meter, it suspends execution for the specified child process. Speci- fies either the process ID or process group ID of the child process. Used with the idtype parameter, it suspends execution for the specified process. Specifies a pointer to a siginfo_t structure. Specifies the conditions that must occur before a wait operation is performed by the waitid() function. DESCRIPTION The waitid() function holds a calling process until the state of a child process changes. The current state of the child is recorded in a structure pointed to by the infop parameter. If a child process changed state prior to the call to the waitid() function, the waitid() function returns immediately. The idtype and id parameters determine which child process the waitid() function is to act upon. If the idtype parameter is P_PID, the waitid() function waits for the child with a process ID equal to (pid_t)id. If the idtype parameter is P_PGID, the waitid() function waits for any child with a process group ID equal to (pid_t)id. If the idtype parameter is P_ALL, the waitid function waits for any child and the id parameter is ignored. The options parameter specifies the conditions that must occur before a wait operation is performed by the waitid() function. To specify a condition, use at least one of the following flags in a logical OR op- eration: Return the status for any child that was stopped and has been continued. Wait for processes to exit. Return immediately if no child processes in the requested state are present. Keep the child process whose status is returned in infop in a waitable state. Another wait for that child may occur with the same results. Wait for and return the process status of any child that has stopped upon receipt of a sig- nal. [Digital] Wait for traced processes to become trapped or reach a breakpoint (see ptrace(2)). The infop parameter must point to a siginfo_t structure as defined in siginfo(5). This structure contains the status explaining why a process is in a wait state. The waitid() function returns if a child process is found that satis- fies the conditions defined by the idtype and options parameters. In this case, the system fills in the structure pointed to by the infop parameter with the process status. The system always sets the si_signo structure member to SIGCHLD. RETURN VALUE If the waitid() function returns because the state of a child process changes, it returns a value of zero (0). Otherwise, a value of -1 is returned and errno is set to indicate the error. ERRORS The waitid() function sets errno to the specified values for the fol- lowing conditions: The calling process has no unwaited-for child processes. [Digital] The infop parameter points to an invalid ad- dress. The waitid() function was interrupted due to the receipt of a signal by the calling process. An invalid value was used with the op- tions parameter, or the idtype and id parameters specify an invalid set of processes. RELATED INFORMATION Functions: intro(2), exec(2), exit(2), fork(2), pause(3), ptrace(2), sigaction(2), signal(2), wait(2) Routines: pause(3) Files: siginfo(5) Standards: standards(5) delim off waitid(2)