SIGUSR1 信号未触发

Question

我开始学习信号以及如何触发它们。我有这个使用 SIGUSR1 触发信号的简单代码，但是当我运行代码时，唯一打印的是“Starting...”行。没有其他东西被打印出来。我做错了什么吗？

#include <signal.h>
#include <stdio.h>

void my_handler(int signum)
{
    printf("Hello\n");
    printf("%d\n", signum);
    if (signum == SIGUSR1) {
        printf("Receveid\n");
    }
}

int main() {
    printf("Starting...\n");
    signal(SIGUSR1, my_handler);
    return 0;
}

Answer 1

signal only registers a signal handler - the function to be called when the process receives a signal. From within your program, you can use raise到向调用进程发送信号。

如果你在 POSIX 环境中，你应该看看 man 7 signal-safety for a list of functions that are safe to call from within signal handlers (additional information in this answer). printf is not included in this list - nor are a lot standard library functions. Its better to use an operation which is atomic with regards to signals, such as write (or reentrant, such as strlen)。

使用 raise 的粗略示例，其中 returns 0 成功，非零错误。

#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

void my_handler(int signum) {
    char msg[] = "SIGUSR1 handler\n";

    if (signum == SIGUSR1)
        write(STDOUT_FILENO, msg, strlen(msg));
}

int main(void) {
    printf("Starting...\n");

    signal(SIGUSR1, my_handler);

    (void) getchar();

    if (raise(SIGUSR1) != 0)
        fprintf(stderr, "Could not raise signal.\n");
}

SIGUSR1 信号未触发

SIGUSR1 Signal is not triggering

c

signals