ls opendir readdir closedir printf
有了上面的信息,我们很容易编写自己的ls命令。
(3)如何编写ls
#include
#include
#include
void show_ls(char filename[]);
int main(int argc,char* argv[])
{
if(argc == 1)
show_ls(".");
while(--argc)
{
printf("%s: \n",*++argv);
show_ls(*argv);
printf("\n");
}
return 0;
}
void show_ls(char filename[])
{
DIR* dir_ptr; //the directory
struct dirent* direntp; //each entry
if((dir_ptr = opendir(filename)) == NULL)
fprintf(stderr,"ls1: cannot open%s \n",filename);
while((direntp = readdir(dir_ptr)) != NULL)
printf("%-10s",direntp->d_name);
closedir(dir_ptr);
}
struct dirent和DIR结构体
1、包含头文件
#include
2、struct dirent 结构
struct dirent
{
long d_ino; /* inode number 索引节点号 */
off_t d_off; /* offset to this dirent 在目录文件中的偏移 */
unsigned short d_reclen; /* length of this d_name 文件名长 */
unsigned char d_type; /* the type of d_name 文件类型 */
char d_name [NAME_MAX+1]; /* file name (null-terminated) 文件名,最长255字符 */
}
3、DIR 结构
struct __dirstream
{
void *__fd; /* `struct hurd_fd' pointer for descriptor. */
char *__data; /* Directory block. */
int __entry_data; /* Entry number `__data' corresponds to. */
char *__ptr; /* Current pointer into the block. */
int __entry_ptr; /* Entry number `__ptr' corresponds to. */
size_t __allocation; /* Space allocated for the block. */
size_t __size; /* Total valid data in the block. */
__libc_lock_define (, __lock) /* Mutex lock for this structure. */
};
typedef struct __dirstream DIR;
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