linux C语言 管道pipe的问题

#include
#include
#include

int main(int argc, const char *argv[])
{
int fd[2];
int pid;

if (argc != 2)
{
printf("Usage:\n\t%s string\n", argv[0]);
return 1;
}

if (pipe(fd) < 0)
{
printf("Unable to create pipe!\n");
return 1;
}

// fork child process
pid = fork();

if (pid == 0) //child
{
close(fd[0]); //close read end
write(fd[1], argv[1], strlen(argv[1])); //write message
close(fd[1]); //close before exit
}
else if (pid > 0) //parent
{
char buf[1024];
int len;

close(fd[1]); //close write end
len = read(fd[0], buf, sizeof(buf)); //read from the pipe
buf[len] ='\0';
printf(" message from child: %s\n", buf);
wait(NULL); //wait for child exit
close(fd[0]); //close before exit
}
else
{
printf("Unable to fork!\n");
return 1;
}

return 0;
}

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