Linux Application Programming: Signal (semaphore) instance 1

1: Sample Code

#include<stdio.h>#include<fcntl.h>#include<unistd.h>#include<stdlib.h>#include<string.h>#include<signal.h>#include<stdlib.h>#include <sys/wait.h>//the copy fie size must>Mint count=0;//current copy numberint file_size;//the file sizepid_t pid;void sig_alarm(int arg){kill(pid,SIGUSR1);}void sig_int(int arg){printf("file size:%d totalreceive size:%d\n",file_size,count);exit(EXIT_SUCCESS);}char bar[10000];void sig_usr(int sig){float i;strcat(bar,"#");    fflush(stdout);i=(float)count/(float)file_size;//printf("curent over :%0.0f%%\n",i*100);printf("curent over :%s %0.0f%%\n",bar,i*100);}int main(int argc,char *argv[]){int i=0,stat_val;;int fd_src,fd_des;char buf[4096];//in order to infirm the problem, buf can set smallif(argc!=3){printf("check the format:comm src_file des_file\n");return -1;}if((fd_src=open(argv[1],O_RDONLY) )==-1 ){perror("open file src");exit(EXIT_FAILURE);}file_size=lseek(fd_src,0,SEEK_END);lseek(fd_src,0,SEEK_SET);if( (fd_des=open(argv[2],O_RDWR|O_CREAT,0644) )==-1 ){perror("open fd_fdes");exit(EXIT_FAILURE);}if( (pid=fork())==-1){perror("fork");exit(EXIT_FAILURE);}else if(pid==0){printf("1pid();%d ppid%d\n",getpid(),getppid());signal(SIGUSR1,sig_usr);do{memset(buf,'\0',sizeof(buf));if((i=read(fd_src,buf,sizeof(buf)))==-1)//the copy number may modify{perror("read");exit(EXIT_FAILURE);}else if(i==0){//perror("kill");kill(getppid(),SIGINT);break;}else{if(write(fd_des,buf,i)==-1){perror("write");exit(EXIT_FAILURE);}count+=i;}}while(i!=0);waitpid(pid,&stat_val,0);if(WIFEXITED(stat_val)){printf("Child exited with code %d count:%d\n", WEXITSTATUS(stat_val),count);}else if (WIFSIGNALED(stat_val)){printf("Child terminated abnormally, signal %d count:%d\n", WTERMSIG(stat_val),count);}exit(EXIT_SUCCESS);}else if(pid>0){signal(SIGALRM,sig_alarm);signal(SIGINT,sig_int);#if 0ualarm(250000,200000);//if alarm ,in sig_alarm function to install again#endifwhile(1){#if 0alarm(1);//if alarm ,in sig_alarm function to install againpause();#endif#if 0kill(pid,SIGUSR1);usleep(250000);#endifkill(pid,SIGUSR1);sleep(2);}exit(EXIT_SUCCESS);}}

2: execution result