ls命令的实现(2)--实现源码

在上一篇博文http://blog.chinaunix.net/space.php?uid=25909722&do=blog&id=2856481中，我们学习了实现ls命令要涉及到的相关的结构体和函数。有了前面的基础，本文我们实实在在的实现ls命令：

#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include <string.h>
#include <time.h>
#include <pwd.h>
#include <grp.h>

void do_ls(char[]);
void do_stat(char*);
void show_file_info(char*, struct stat*);
void mode_str(int, char[]);
char *uid_str(uid_t);
char *gid_str(gid_t);

int main(int argc, char *argv[])
{
        if(argc == 1)
                do_ls(".");
        else
                while(--argc){
                        printf("%s:\n", *++argv);
                        do_ls(*argv);
                }

        return 0;
}

void do_ls(char dirname[])
{
        DIR     *dir_ptr;           /* the directory */
        struct dirent   *direntp;       /* each entry */
        char    full_path[256];

        if((dir_ptr = opendir(dirname)) == NULL){
                fprintf(stderr, "ls2: cannot open %s\n", dirname);
        }else{
                while((direntp = readdir(dir_ptr)) != NULL){
                        strcpy(full_path, dirname);
                        int dir_len = strlen(dirname);
                        if(dirname[dir_len - 1] != '/'){  /* 处理目录字符串最后没有‘/’的情况 */
                                full_path[dir_len] = '/';
                                strcpy(full_path + dir_len + 1, direntp->d_name);
                        }else
                                strcpy(full_path + dir_len, direntp->d_name);

                        do_stat(full_path);
                }
                closedir(dir_ptr);
        }
}
void do_stat(char *filename) /* 获得目录中文件的相关信息 */
{
        struct stat     info;

        /* 如果filename最后没有‘/’的话，stat调用失败 */
        if(stat(filename, &info) == -1){        /* cannot stat */
                perror("stat"); /* say why */
                printf("filename:%s\n", filename);
        }else{
                char *pname = strrchr(filename, '/');
                show_file_info(pname + 1, &info);
        }
}

void show_file_info(char *filename, struct stat *info_p) /* 打印文件的相关信息 */
{
        char    modestr[11];

        mode_str(info_p->st_mode, modestr);

        printf("%s", modestr);
        printf("%3d ", (int)info_p->st_nlink);
        printf("%-8s", uid_str(info_p->st_uid));
        printf("%-8s", gid_str(info_p->st_gid));
        printf("%4ld ", (long)info_p->st_size);
        printf("%.12s ", 4 + ctime(&info_p->st_mtime));
        printf("%s\n", filename);
}

void mode_str(int mode, char str[]) /* 将文件的相关信息转化成 “crw-rw---"的形式 */
{
        strcpy(str, "----------");      /* default = no perms */
        if(S_ISDIR(mode))       str[0] = 'd';   /* directory */
        if(S_ISCHR(mode))       str[0] = 'c';   /* char device */
        if(S_ISBLK(mode))       str[0] = 'b';   /* block device */
        if(S_ISLNK(mode))       str[0] = 'l';

        if(mode & S_IRUSR)      str[1] = 'r';   /* 3 bits for user */
        if(mode & S_IWUSR)      str[2] = 'w';
        if(mode & S_IXUSR)      str[3] = 'x';

        if(mode & S_IRGRP)      str[4] = 'r';   /* 3 bits for group */
        if(mode & S_IWGRP)      str[5] = 'w';
        if(mode & S_IXGRP)      str[6] = 'x';

        if(mode & S_IROTH)      str[7] = 'r';   /* 3 bits for other */
        if(mode & S_IWOTH)      str[8] = 'w';
        if(mode & S_IXOTH)      str[9] = 'x';
}

char *uid_str(uid_t uid) /* 将uid转化成username */
{
        static char     numstr[10];
        struct passwd   *pw_ptr;

        if((pw_ptr = getpwuid(uid)) == NULL){
                sprintf(numstr, "%d", uid);
                return numstr;
        }else
                return pw_ptr->pw_name;
}

char *gid_str(gid_t gid) /* 将gid转化成groupname */
{
        static char     numstr[10];
        struct group    *grp_ptr;

        if((grp_ptr = getgrgid(gid)) == NULL){
                sprintf(numstr, "% d", gid);
                return numstr;
        }else
                return grp_ptr->gr_name;
}

编译和运行结果：

digdeep@ubuntu:~/uulp$ gcc -Wall -o ls1 ls1.c

digdeep@ubuntu:~/uulp$ ./ls1  /etc/network/

/etc/network/:

drwxr-x---  2 root    root     4096 Apr 26 07:03 if-down.d

drwxr-x---  2 root    root     4096 Jul 14 10:47 if-up.d

drwxr-x---  2 root    root     4096 Apr 26 07:05 if-pre-up.d

drwxr-x---  6 root    root     4096 Jun 14 05:34 .

drwxr-x---  2 root    root     4096 Apr 26 07:05 if-post-down.d

-rwrr-----   1 root    root      196 Jun 14 05:33 interfaces

drwxr-x---147 root    root    12288 Sep 19 20:33 ..