改进ls的实现

改进后代码：

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <dirent.h>
#include <string.h>
#include <linux/limits.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>

#define PARAM_NONE 0 //无参数
#define PARAM_A    1 //-a
#define PARAM_L    2 //-l
#define MAXROWLEN  80 //一行最多显示的字符数

int g_leave_len = MAXROWLEN; //一行是剩余长度，用于输出对齐
int g_maxlen;                //存放某目录下最长文件名的长度

void my_error(const char* errstring, int line)
{
    fprintf(stderr,"line:%d",line);
    perror(errstring);
    exit(1);
}

//打印单个文件，且没有-l参数
void display_single(char *name)
{
    int i,len;
    //如果本行不足以打印一个文件名则换行
    if(g_leave_len < g_maxlen)
    {
        printf("\n");
        g_leave_len = MAXROWLEN;
    }
    
    len = strlen(name);
    len = g_maxlen - len;
    
    printf("%-s",name);

    for(i=0;i<len;i++)
    {
        printf(" ");
    }
    printf(" ");

    g_leave_len = g_leave_len - g_maxlen - 2;

}

/*获取文件属性并打印*/
void display_attribute(struct stat buf, char *name)
{
    char buf_time[32];
    struct passwd *psd;
    struct group *grp;
    
    //获取文件类型
    if(S_ISLNK(buf.st_mode))
        printf("1");
    else if(S_ISREG(buf.st_mode))
        printf("-");
    else if(S_ISDIR(buf.st_mode))
        printf("d");
    else if(S_ISCHR(buf.st_mode))
        printf("c");
    else if(S_ISBLK(buf.st_mode))
        printf("b");
    else if(S_ISFIFO(buf.st_mode))
        printf("f");
    else if(S_ISSOCK(buf.st_mode))
        printf("s");

    //获取文件权限
    if(buf.st_mode & S_IRUSR)
        printf("r");
    else
        printf("-");
    if(buf.st_mode & S_IWUSR)
        printf("w");
    else
        printf("-");
    if(buf.st_mode & S_IXUSR)
        printf("x");
    else
        printf("-");

    if(buf.st_mode & S_IRGRP)
        printf("r");
    else
        printf("-");
    if(buf.st_mode & S_IWGRP)
        printf("w");
    else
        printf("-");
    if(buf.st_mode & S_IXGRP)
        printf("x");
    else
        printf("-");

    if(buf.st_mode & S_IROTH)
        printf("r");
    else
        printf("-");
    if(buf.st_mode & S_IWOTH)
        printf("w");
    else
        printf("-");
    if(buf.st_mode & S_IXOTH)
        printf("x");
    else
        printf("-");

    printf("  ");
    
    //根据uid和gid获取文件所有者的用户名于组名
    psd = getpwuid(buf.st_uid);
    grp = getgrgid(buf.st_gid);
    printf("%4ld",buf.st_nlink);
    printf("%-8s",psd->pw_name);
    printf("%-9s",grp->gr_name);
    
    printf("%6ld",buf.st_size);
    strcpy(buf_time, ctime(&buf.st_mtime));//将格林位置时间转化成正常时间格式
    buf_time[strlen(buf_time) - 1] = 0;
    printf(" %s",buf_time);
}

//根据flag参数显示文件内容，调用display_single或者display_attribute
void display(int flag,char *pathname)
{
    int i,j;
    struct stat buf;
    char name[NAME_MAX + 1];

    for(i=0,j=0;i<strlen(pathname);i++)
    {
        if(pathname[i] == '/')
        {
            j = 0;
        }
        else
            name[j++] = pathname[i];
    }
    name[j] = 0;

    if(lstat(pathname,&buf) == -1)
    {
        my_error("stat",__LINE__);
    }
    
    if(flag == PARAM_NONE)
    {
        if(name[0] != '.')//不显示隐藏文件
        {
            display_single(name);
        }
    }
    else if(flag == PARAM_A)
    {
        display_single(name);
    }
    else if(flag == PARAM_L)
    {
        if(name[0] != '.')
        {
            display_attribute(buf,name);
            printf(" %-s\n",name);
        }
    }
    else if(flag == (PARAM_A | PARAM_L))
    {
        display_attribute(buf,name);
        printf(" %-s\n",name);
    }

}

void display_dir(int flag_param,const char *path)
{
    DIR* dir;
    struct dirent* dirent;
    char filenames[256][PATH_MAX+1],temp[PATH_MAX+1];
    int count = 0;//总共有多少个文件

    if((dir = opendir(path)) == NULL)
    {
        my_error("opendir",__LINE__);
    }
    
    //获取文件总数和最长文件名
    while((dirent = readdir(dir)) != NULL)
    {
        if(g_maxlen < strlen(dirent->d_name))
            g_maxlen = strlen(dirent->d_name);
        count++;
    }
    closedir(dir);
    
    if(count>256)
        my_error("文件太多超过了256个",__LINE__);
    
    int i,j,len = strlen(path);
    //获取目录下所有的文件名
    dir = opendir(path);
    for(i=0;i<count;i++)
    {
        dirent = readdir(dir);
        if(dirent == NULL)
        {
            my_error("readdir",__LINE__);    
        }
        strncpy(filenames[i],path,len);
        filenames[i][len] = 0;
        strcat(filenames[i],dirent->d_name);
        filenames[i][len+strlen(dirent->d_name)] = 0;
    }

    //对文件名进行排序
    for(i=0;i<count-1;i++)
        for(j=i+1;j<count-1;j++)
        {
            if(strcmp(filenames[i],filenames[j]) > 0)
            {
                strcpy(temp,filenames[j]);
                strcpy(filenames[j] , filenames[i]);
                strcpy(filenames[i] , temp);
            }
        }

    for(i=0;i<count;i++)
        display(flag_param,filenames[i]);
    closedir(dir);
    
    //没有-l的话打印一个换行符
    if((flag_param & PARAM_L) == 0)
        printf("\n");
}

int main(int argc, char **argv)
{
    int i,j,k;
    int num;//记录-的个数
    char path[PATH_MAX + 1];
    char param[32]; // 保存命令行参数
    int  flag_param = PARAM_NONE;
    struct stat buf;
    
    j = 0;
    num = 0;
    for(i=1;i<argc;i++)
    {
        if(argv[i][0] == '-')
        {
            for(k=1;k<strlen(argv[i]);k++)
            {
                param[j] = argv[i][k];
                j++;
            }
            num++;
        }
    }

    //现在只支持-a和-l参数
    for(i=0;i<j;i++)
    {
        if(param[i] == 'a')
        {
            flag_param |= PARAM_A;
        }
        else if(param[i] == 'l')
        {
            flag_param |= PARAM_L; 
        }
        else
        {
            printf("错误的参数：%c\n",param[i]);
            exit(1);
        }
    }

    param[j] = 0;

    //如果没有输入文件名或者目录，就显示当前目录
    if((num + 1) == argc)
    {
        strcpy(path,"./");
        path[2] = 0;
        display_dir(flag_param,path);
        return 0;
    }
    
    i = 1;
    for(i=1;i<argc;i++)
    {
        if(argv[i][0] != '-')
        {
            strcpy(path,argv[i]);
            if(stat(path,&buf) == -1)
                my_error("stat",__LINE__);
            if(S_ISDIR(buf.st_mode))
            {
                //判断目录是否以/结尾
                if(path[strlen(argv[i]) - 1] != '/')
                {
                    path[strlen(argv[i])] = '/';
                    path[strlen(argv[i] + 1)] = 0; 
                }
                else
                    path[strlen(argv[i])] = 0; 
            
                display_dir(flag_param,path);
            }
            else
            {
                display(flag_param,path);
            }
        }
    }

    return 0;     
}

码云链接：https://gitee.com/wu-zhuohang/codes/hpr8vj26k7n459uiwgoqz62

运行结果截图：