ls（1）命令的简单实现（一）

这个命令主要利用opendir函数读出DIR结构体，然后用readdir函数读出struct dirent结构体，最后利用dirent结构体里面的d_name来用lstat函数读出文件的各种属性，最后格式化输出，下面的代码主要实现了无参数的默认文件名输出，还有实现了带‘-l’参数的属性输出，目前只是实现了‘-l’参数，以后再努力实现其他参数。

/********************************************************  Program:List all the file of the directory.  History: 2013/04/08  dingdong  First release2013/05/21  dingdong  Second release[not finish]2013/05/24  dingdong  Third release[finish '-l']*********************************************************/#include "apue.h"#include <dirent.h>#include <pwd.h>#include <grp.h>#include <time.h>voidparameters_l(char *temp);/*'-l' parameter*/int main(int argc,char *argv[]){DIR*dp;struct  dirent*dirp;inti,j,k=0,count=0;/*count for format,per 5 d_name print '\n'*/intflag1=0,flag2=0;/*flag2 for extra parameters           flag1 check have parameters or not, */char buf[10];if(argc==1)/*current directory by default*/argv[1]=".";else if(argc>=2){if(argv[1][0]=='-')flag1=1;else flag1=0;}if(flag1&&argc==2)/*have no parameters and argc==2*/argv[2]=".";if(flag1)/*have parameters*/{for(i=1;i<argc;i++){for(j=0;argv[i][j]!='\0';j++){if(argv[i][j]!='-')/*collect the parameters*/{buf[k]=argv[i][j];k++;}}}buf[k]='\0';for(k=0;buf[k]!='\0';k++){switch(buf[k]){case 'l':parameters_l(argv[2]);break;default :flag2=1; printf("%s: extra operand %s\n",argv[0],argv[1]);  break;}if(flag2)break;/*if have extra operand then break*/}}/*if(flag2)*/else if(!flag1)/*not parameters*/ {if((dp=opendir(argv[1]))==NULL)err_sys("can't open %s",argv[1]);while((dirp=readdir(dp))!=NULL){printf("%-12s  ",dirp->d_name);count++;if(count==7){count=0;printf("\n");}}printf("\n");closedir(dp);}exit(0);}void parameters_l(char *temp){DIR *dp;struct dirent   *dirp;struct stat     buf;struct passwd*uid;struct group*gid;char*time;/*for ctime */if((dp=opendir(temp))==NULL)err_sys("can't open %s",temp);while((dirp=readdir(dp))!=NULL){char mode[]="----------.";if(lstat(dirp->d_name,&buf)<0)err_ret("lstat error");/*file type*/if(S_ISDIR(buf.st_mode))mode[0]='d';/*directory*/if(S_ISCHR(buf.st_mode))mode[0]='b';/*block special file*/if(S_ISBLK(buf.st_mode))mode[0]='c';/*character special file*/if(S_ISFIFO(buf.st_mode))mode[0]='f';/*FIFO*/if(S_ISLNK(buf.st_mode))mode[0]='s';/*socket*/if(S_ISSOCK(buf.st_mode))mode[0]='l';/*symbolic link*//*the mode of the file*/if(buf.st_mode&S_IRUSR)mode[1]='r';if(buf.st_mode&S_IWUSR)mode[2]='w';if(buf.st_mode&S_IXUSR)mode[3]='x';if(buf.st_mode&S_IRGRP)mode[4]='r';if(buf.st_mode&S_IWGRP)mode[5]='w';if(buf.st_mode&S_IXGRP)mode[6]='x';if(buf.st_mode&S_IROTH)mode[7]='r';if(buf.st_mode&S_IWOTH)mode[8]='w';if(buf.st_mode&S_IXOTH)mode[9]='x';/*user and group*/if((uid=getpwuid(buf.st_uid))==NULL)err_sys("getpwuid error");if((gid=getgrgid(buf.st_gid))==NULL)err_sys("getgrgid error");/*ctime for file*/time=ctime(&buf.st_ctime);time[strlen(time)-1]='\0';/*ignore the '\n'*/printf("%s %-2d %-8s %-8s %-5d %-1s %-5s\n",mode,buf.st_nlink,uid->pw_name,gid->gr_name,buf.st_size,time,dirp->d_name);}closedir(dp);}