八十五. 读取指定目录下的普通文件的个数——代码
getfilenummer.c
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <dirent.h>
#include <sys/types.h>
int get_file_num(char* root)
{
int total = 0;
DIR* dir = NULL;
// 打开目录
dir = opendir(root);
// 循环从目录中读文件
char path[1024];
// 定义记录xiang指针
struct dirent* ptr = NULL;
while( (ptr = readdir(dir)) != NULL)
{
// 跳过. 和 ..
if(strcmp(ptr->d_name, ".") == 0 || strcmp(ptr->d_name, "..") == 0)
{
continue;
}
// 判断是不是目录
if(ptr->d_type == DT_DIR)
{
sprintf(path, "%s/%s", root, ptr->d_name);
// 递归读目录
total += get_file_num(path);
}
// 如果是普通文件
if(ptr->d_type == DT_REG)
{
total ++;
}
}
closedir(dir);
return total;
}
int main(int argc, char* argv[])
{
if(argc < 2)
{
printf("./a.out path");
exit(1);
}
int total = get_file_num(argv[1]);
printf("%s has regfile number: %d\n", argv[1], total);
return 0;
}
运行一下:
[root@VM_0_15_centos dir_op]# ls
chdir.c mkdir.c opendir.c readfileNum.c
[root@VM_0_15_centos dir_op]# gcc readfileNum.c
[root@VM_0_15_centos dir_op]# ./a.out
./a.out path[root@VM_0_15_centos dir_op]# ./a.out ./
./ has regfile number: 5
[root@VM_0_15_centos dir_op]# ./a.out /home
/home has regfile number: 6206
八十六. dup和dup2函数
八十七. dup和dup2测试
接下来看dup和dup2的例子
dup.c
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#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
int main(void)
{
int fd = open("temp", O_RDWR | O_CREAT, 0664);
if(fd == -1)
{
perror("open");
exit(1);
}
// 复制文件描述符
// int fd2 = dup(fd);
int fd2 = fcntl(fd, F_DUPFD);
// 写文件
char* p = "让编程改变世界。。。。。。";
write(fd2, p, strlen(p));
close(fd2);
char buf[1024];
lseek(fd, 0, SEEK_SET);
read(fd, buf, sizeof(buf));
printf(" buf = %s\n", buf);
close(fd);
return 0;
}
dup2.c
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
int main(void)
{
int fd = open("temp", O_RDWR | O_CREAT | O_APPEND, 0664);
if(fd == -1)
{
perror("open");
exit(1);
}
int fd2 = open("temp1", O_RDWR | O_CREAT | O_APPEND, 0664);
if(fd2 == -1)
{
perror("open open");
exit(1);
}
// 复制文件描述符
dup2(fd, fd2);
// 写文件
char* p = "change the world by programing。。。。。。";
write(fd2, p, strlen(p));
close(fd2);
char buf[1024];
lseek(fd, 0, SEEK_SET);
read(fd, buf, sizeof(buf));
printf(" buf = %s\n", buf);
close(fd);
return 0;
}