//父子进程信号通信//signal 接收信号//kill 发送信号[root@localhost chapter11]# cat alarm.c /* In alarm.c, the first function, ding, simulates an alarm clock. */#include <signal.h>#include <stdio.h>#include <unistd.h>#include <stdlib.h>static int alarm_fired = 0;void ding(int sig){ alarm_fired = 1;}/* In main, we tell the child process to wait for five seconds before sending a SIGALRM signal to its parent. */int main(){ pid_t pid; printf("alarm application starting\n"); pid = fork(); switch(pid) { case -1: /* Failure */ perror("fork failed"); exit(1); case 0: /* child */ sleep(5); kill(getppid(), SIGALRM); exit(0); }/* The parent process arranges to catch SIGALRM with a call to signal and then waits for the inevitable. */ printf("waiting for alarm to go off \n"); (void) signal(SIGALRM, ding); pause(); if (alarm_fired) printf("Ding!\n"); printf("done\n"); exit(0);}[root@localhost chapter11]# ./alarm alarm application startingwaiting for alarm to go off Ding!done[root@localhost chapter11]# 另一个接收信号的函数 sigaction
[root@localhost chapter11]# cat ctrlc2.c #include <signal.h>#include <stdio.h>#include <unistd.h>void ouch(int sig){ printf("OUCH! - I got signal %d\n", sig);}int main(){ struct sigaction act; act.sa_handler = ouch; sigemptyset(&act.sa_mask); act.sa_flags = 0; sigaction(SIGINT, &act, 0); while(1) { printf("Hello World!\n"); sleep(1); }}[root@localhost chapter11]# ./ctrlc2Hello World!Hello World!^COUCH! - I got signal 2Hello World!^COUCH! - I got signal 2Hello World!^COUCH! - I got signal 2Hello World!^COUCH! - I got signal 2Hello World!^COUCH! - I got signal 2Hello World!^COUCH! - I got signal 2Hello World!Hello World!Hello World!Hello World!^COUCH! - I got signal 2Hello World!Hello World!Hello World!^\Quit (core dumped)[root@localhost chapter11]# 常用信号:
[root@localhost chapter11]# cat /usr/include/bits/signum.h /* Signal number definitions. Linux version. Copyright (C) 1995,1996,1997,1998,1999,2003 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */#ifdef_SIGNAL_H/* Fake signal functions. */#define SIG_ERR((__sighandler_t) -1)/* Error return. */#define SIG_DFL((__sighandler_t) 0)/* Default action. */#define SIG_IGN((__sighandler_t) 1)/* Ignore signal. */#ifdef __USE_UNIX98# define SIG_HOLD((__sighandler_t) 2)/* Add signal to hold mask. */#endif/* Signals. */#defineSIGHUP1/* Hangup (POSIX). */#defineSIGINT2/* Interrupt (ANSI). */#defineSIGQUIT3/* Quit (POSIX). */#defineSIGILL4/* Illegal instruction (ANSI). */#defineSIGTRAP5/* Trace trap (POSIX). */#defineSIGABRT6/* Abort (ANSI). */#defineSIGIOT6/* IOT trap (4.2 BSD). */#defineSIGBUS7/* BUS error (4.2 BSD). */#defineSIGFPE8/* Floating-point exception (ANSI). */#defineSIGKILL9/* Kill, unblockable (POSIX). */#defineSIGUSR110/* User-defined signal 1 (POSIX). */#defineSIGSEGV11/* Segmentation violation (ANSI). */#defineSIGUSR212/* User-defined signal 2 (POSIX). */#defineSIGPIPE13/* Broken pipe (POSIX). */#defineSIGALRM14/* Alarm clock (POSIX). */#defineSIGTERM15/* Termination (ANSI). */#defineSIGSTKFLT16/* Stack fault. */#defineSIGCLDSIGCHLD/* Same as SIGCHLD (System V). */#defineSIGCHLD17/* Child status has changed (POSIX). */#defineSIGCONT18/* Continue (POSIX). */#defineSIGSTOP19/* Stop, unblockable (POSIX). */#defineSIGTSTP20/* Keyboard stop (POSIX). */#defineSIGTTIN21/* Background read from tty (POSIX). */#defineSIGTTOU22/* Background write to tty (POSIX). */#defineSIGURG23/* Urgent condition on socket (4.2 BSD). */#defineSIGXCPU24/* CPU limit exceeded (4.2 BSD). */#defineSIGXFSZ25/* File size limit exceeded (4.2 BSD). */#defineSIGVTALRM26/* Virtual alarm clock (4.2 BSD). */#defineSIGPROF27/* Profiling alarm clock (4.2 BSD). */#defineSIGWINCH28/* Window size change (4.3 BSD, Sun). */#defineSIGPOLLSIGIO/* Pollable event occurred (System V). */#defineSIGIO29/* I/O now possible (4.2 BSD). */#defineSIGPWR30/* Power failure restart (System V). */#define SIGSYS31/* Bad system call. */#define SIGUNUSED31#define_NSIG65/* Biggest signal number + 1 (including real-time signals). */#define SIGRTMIN (__libc_current_sigrtmin ())#define SIGRTMAX (__libc_current_sigrtmax ())/* These are the hard limits of the kernel. These values should not be used directly at user level. */#define __SIGRTMIN32#define __SIGRTMAX(_NSIG - 1)#endif/* <signal.h> included. */[root@localhost chapter11]#
信号值动作解释SIGHUP1终端线路挂断SIGINT2Term键盘输入的中断命令，从终端输入 Ctrl-C 时发生SIGQUIT3Core键盘输入的退出命令SIGILL4Core错误指令SIGABRT6Coreabort(3)发出的中止信号SIGFPE8Core浮点数异常SIGKILL9TermKILL信号SIGSEGV11Core非法内存访问SIGPIPE13Term管道断开SIGALRM14Termalarm(2)发出的中止信号SIGTERM15Term强制中止信号SIGUSR130,10,16Term用户自定义信号1SIGUSR231,12,17Term用户自定义信号2SIGCHLD20,17,18Ign子进程中止信号SIGCONT19,18,25Cont继续执行一个停止的进程SIGSTOP17,19,23Stop非终端来的停止信号SIGTSTP18,20,24Stop终端来的停止信号SIGTTIN21,21,26Stop后台进程读终端SIGTTOU22,22,27Stop后台进程写终端refer tohttp://tech.idv2.com/2006/09/28/useful-linux-signals/
