pipe fifo

#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

int main(){
int pipe_fd[2];
if(pipe(pipe_fd) < 0){
printf("pipe create error\n");
return -1;
}else{
printf("pipe create success\n");
close(pipe_fd[0]);
close(pipe_fd[1]);
}
}
--------------------------------------------
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

int main(){
int pipe_fd[2];
pid_t pid;
char buf_r[100];
char *p_wbuf;
int r_num;
memset(buf_r,0,sizeof(buf_r)); //清零
if(pipe(pipe_fd)<0){
printf("pipe create error\n");
return -1;
}
if((pid = fork())==0){
printf("\n");
close(pipe_fd[1]);
sleep(2);
if((r_num=read(pipe_fd[0],buf_r,100))>0){
printf("%d numbers read from the pipe is %s\n",r_num,buf_r);
}
close(pipe_fd[0]);
exit(0);
}else if(pid > 0){
close(pipe_fd[0]);
if(write(pipe_fd[1],"Hello",5)!=-1)
printf("parent write1 success!\n");
if(write(pipe_fd[1],"Pipe",5)!=-1)
printf("parent write2 success!\n");
close(pipe_fd[1]);
sleep(3);
waitpid(pid,NULL,0); //等待子进程退出
exit(0);
}
}
-----------------------------------------
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#define BUFSIZE 1024
int main(){
FILE *fp;
char *cmd = "ps -ef";
char buf[BUFSIZE];
buf[BUFZISE] = '\0';
if((fp = popen(cmd,"r")) == NULL)
perror("popen");
while((fgets(buf,BUFSIZE,fp))!=NULL)
printf("%s",buf);
pclose(fp);
exit(0);
}
------------------------------------------
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#define FIFO "/tmp/myfifo"

main(int argc,char** argv){
char buf_r[100];
int fd;
int nread;
if((mkfifo(FIFO,O_CREAT|O_EXCL)<0)&&(errno!=EEXIST)){
printf("cannot create fifoserver\n");
}
printf("Preparing for reading bytes...\n");

fd = open(FIFO,O_RDONLY|O_NONBLOCK,0);
if(fd==-1){
perror("open");
exit(1);
}

memset(buf_r,0,sizeof(buf_r));
while(1){
memset(buf_r,0,sizeof(buf_r));
if((nread = read(fd,buf_r,100))==-1){
if(errno==EAGAIN){
printf("no data yet\n");
}
}
printf("read %s from FIFO\n",buf_r);
sleep(1);
}
pause();
unlink(FIFO);
}
----------------------------------------------
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define FIFO_SERVER "/tmp/myfifo"

main(int argc,char** argv){
int fd;
char w_buf[100];
int nwrite;
if(fd == -1){
if(errno == ENXIO){
printf("open error;no reading process\n");
}
}
fd = open(FIFO_SERVER,O_WRONLY|O_NONBLOCK,0);
if(argc == 1){
printf("Please send something\n");
}
strcpy(w_buf,argv[1]);
if((nwrite = write(fd,w_buf,100))==-1){
if(errno == EAGAIN){
printf("The FIFO has not been read yet,Please try later\n");
}
}else{
printf("write %s to the FIFO\n",w_buf);
}

}