The wait() and waitpid() interfaces set a status value of type int packed as a bitfield with various types of child termination information. Returns: If status information is available prior to the call to waitpid(), the return is immediate. The call wait(&status) is equivalent to: waitpid(-1, &status, 0); The waitpid() system call suspends execution of the calling process until a child specified by pid argument has changed state. The older wait3 () call is the same as wait4 () with a wpid value of -1. In this case, the return value is 0. waitpid() behaves identically to wait() if pid has a value of -1 and options has a value of zero. Note: . During the execution of all subprocesses, the main * process will be hung until all subprocesses exit . If status information is available prior to the call to waitpid(), the return is immediate. So the exit status of main * process depends on the two subprocesses.
[wait&waitpid状态值] 1. python 中 os.system 的返回值的format与wait的返回值status一致: On Unix, the return value is the exit status of the process encoded in the format specified for wait() os.system直到命令进程执行完毕才返回, SIGSTOP把子进程暂停, os.system也依旧阻塞 The waitpid() function behaves the same as wait() when passed a pid argument of -1, and the options argument has a value of zero. Only one of the WIFEXITED(stat_val) and WIFSIGNALED(stat_val) macros can evaluate to a nonzero value. Description: The waitpid() function suspends execution of the calling thread until status information from one of its terminated child processes is available, or until the delivery of a signal whose action is either to terminate the process or execute a signal handler. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. The waitpid function will not block if a child specified by pid is not immediately available. The signature of waitpid() is : pid_t waitpid(pid_t pid, int *status, int options); By default, waitpid() waits only for terminated children, but this behavior is modifiable via the options argument, as described below. waitpid系统调用在Linux函数库中的原型是：#include #include pid_t waitpid(pid_t pid,int *status,int options)从本质上讲，系... chenyu 01-13 1万+ The value of pid can be: < -1 : Wait for any child process whose process group ID is equal to the absolute value … If the implementation supports job control, the status of any child specified by pid that has stopped, and whose status has
waitpid(pid, &status, options) 获取进程退出状态时踩过的坑 ... (** ## If failure, the return value is -1 **). The following macros may be used to test the manner of exit of the pro- … Otherwise, the behavior of waitpid() is modified by the values of pid and options as follows: pid specifies a set of child processes for which status is requested. pcntl_waitpid() will store status information in the status parameter which can be evaluated using the following functions: pcntl_wifexited(), pcntl_wifstopped(), pcntl_wifsignaled(), pcntl_wexitstatus(), pcntl_wtermsig() and pcntl_wstopsig(). Welcome to LinuxQuestions.org, a friendly and active Linux Community. WUNTRACED. If wait() or waitpid() returns because the status of a child process is available, these functions shall return a value equal to the process ID of the child process for which status is reported.
You are currently viewing LQ as a guest. Specifying -1 as the pid is equivalent to the functionality pcntl_wait() provides (minus options).. status. The waitpid call is identical to wait4 with an rusage value of zero.