进程间通讯代码实例以及相关函数释义

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

#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：

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

    #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

#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