进程间通讯代码实例以及相关函数释义

练习：用户设计两个程序，要求进程A中自定义信号SIGUSR1的相应借口，要求进程B每隔一段时间向进程A发送SIGUSR1信号，测试进程A是否可以执行关联的相应接口。

一、processA中设置信号处理handler

c 复制代码

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

// 信号处理函数
void handler(int sig)
{
    switch (sig)
    {
        case SIGUSR1:
            printf("收到user1信号\n");
            break;
        default:
            break;
    }
}

int main(int argc, char const *argv[])
{
    signal(SIGUSR1, handler); // 设置信号处理函数
    while (1);
    return 0;
}

linux手册第七章的signal词条，用户可以自定义信号行为的有两个，SIGUSR1 和SIGUSR2 ，这里自定义SIGUSR1：

复制代码

   Signal      Standard   Action   Comment
   ────────────────────────────────────────────────────────────────────────
   SIGABRT      P1990      Core    Abort signal from abort(3)
   SIGALRM      P1990      Term    Timer signal from alarm(2)
   SIGBUS       P2001      Core    Bus error (bad memory access)
   SIGCHLD      P1990      Ign     Child stopped or terminated
   SIGCLD         -        Ign     A synonym for SIGCHLD
   SIGCONT      P1990      Cont    Continue if stopped
   SIGEMT         -        Term    Emulator trap
   SIGFPE       P1990      Core    Floating-point exception
   SIGHUP       P1990      Term    Hangup detected on controlling terminal
                                   or death of controlling process
   SIGILL       P1990      Core    Illegal Instruction
   SIGINFO        -                A synonym for SIGPWR
   SIGINT       P1990      Term    Interrupt from keyboard
   SIGIO          -        Term    I/O now possible (4.2BSD)
   SIGIOT         -        Core    IOT trap. A synonym for SIGABRT
   SIGKILL      P1990      Term    Kill signal
   SIGLOST        -        Term    File lock lost (unused)
   SIGPIPE      P1990      Term    Broken pipe: write to pipe with no
                                   readers; see pipe(7)
   SIGPOLL      P2001      Term    Pollable event (Sys V);
                                   synonym for SIGIO
   SIGPROF      P2001      Term    Profiling timer expired
   SIGPWR         -        Term    Power failure (System V)
   SIGQUIT      P1990      Core    Quit from keyboard
   SIGSEGV      P1990      Core    Invalid memory reference

   SIGSTKFLT      -        Term    Stack fault on coprocessor (unused)
   SIGSTOP      P1990      Stop    Stop process
   SIGTSTP      P1990      Stop    Stop typed at terminal
   SIGSYS       P2001      Core    Bad system call (SVr4);
                                   see also seccomp(2)
   SIGTERM      P1990      Term    Termination signal
   SIGTRAP      P2001      Core    Trace/breakpoint trap
   SIGTTIN      P1990      Stop    Terminal input for background process
   SIGTTOU      P1990      Stop    Terminal output for background process
   SIGUNUSED      -        Core    Synonymous with SIGSYS
   SIGURG       P2001      Ign     Urgent condition on socket (4.2BSD)
   SIGUSR1      P1990      Term    User-defined signal 1
   SIGUSR2      P1990      Term    User-defined signal 2
   SIGVTALRM    P2001      Term    Virtual alarm clock (4.2BSD)
   SIGXCPU      P2001      Core    CPU time limit exceeded (4.2BSD);
                                   see setrlimit(2)
   SIGXFSZ      P2001      Core    File size limit exceeded (4.2BSD);
                                   see setrlimit(2)
   SIGWINCH       -        Ign     Window resize signal (4.3BSD, Sun)

linux第2章说明了signal函数的使用：

SIGNAL(2) Linux Programmer's Manual SIGNAL(2)

NAME

signal - ANSI C signal handling

SYNOPSIS
c 复制代码
    #include <signal.h>   
	typedef void (*sighandler_t)(int);

    sighandler_t signal(int signum, sighandler_t handler);
DESCRIPTION

signal() sets the disposition of the signal signum to handler, which is either SIG_IGN, SIG_DFL, or the address of a programmer-defined function (a "signal handler").

sighandler _t 规定了传入的信号处理函数的类型，内部为信号传参，返回值为void。当程序收到SIGUSR1信号时handler就会被触发。

二、processB中发送信号

c 复制代码

#include <sys/types.h>
#include <signal.h>
#include <unistd.h>

int main(int argc, char const *argv[])
{

    while (1)
    {
        kill(4778, SIGUSR1);  // 提前查询A进程的进程pid
        sleep(1);
    }
    return 0;
}

man 2 kill：

KILL(2) Linux Programmer's Manual KILL(2)

NAME

kill - send signal to a process

SYNOPSIS

#include <sys/types.h>

#include <signal.h>

int kill(pid_t pid, int sig);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

kill(): _POSIX_C_SOURCE

DESCRIPTION

The kill() system call can be used to send any signal to any process group or process.

测试程序

dada@dada-virtual-machine:~/test$ ./processA

收到user1信号

收到user1信号

收到user1信号

收到user1信号

收到user1信号

收到user1信号

...

测试成功