jerry.c

用五个实例来解释linux下的c编程

/* jerry.c v2.0 */

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>

#define FILE "message.txt"
#define CHILD_MSG "I am Mickey.\n"
#define FATHER_MSG "I am Jerry.\n"

int main()
{
  int fd;
  char buf[BUFSIZ];
  ssize_t s;

  /* Open file for read. */
  fd = open(FILE, O_RDONLY, 0666);
  if(fd < 0) {
    perror("open");
  }
  /* Read message. */
  do {
    s = read(fd, &buf, BUFSIZ);
    write(STDOUT_FILENO, &buf, s);
  } while (s>0);
  /* Close file. */
  close(fd);

  if(fork() == 0) {
    write(STDOUT_FILENO, CHILD_MSG, sizeof(CHILD_MSG)-1);
  } else {
    wait(NULL); 		/* wait for any child exit. */
    write(STDOUT_FILENO, FATHER_MSG, sizeof(FATHER_MSG)-1);
  }
  
  exit(EXIT_SUCCESS);
}