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代码如下:

#include”apue.h”

int userlogin(struct passwd **);

int main()

{

int ret,i=0;

 long ret_cwd;

 struct passwd *pw;

 char buf[128],hostname[16],usercwd[128];

 char *ptmp1;

 do{

ret = userlogin(&pw);

 }while(ret != 1);

 getchar();

 while(1){

//to gethostname

  if(gethostname(buf,128)!=0){

perror(“gethostname()”);

   return 0;

  }

//truncate hostname untill .

  while(buf[i]!=.){

   hostname[i++] = buf[i];

  }

i = 0;

//if the user is root the symbol is #

//else $

//and the current work path is truncated from the last / to the end

  ret_cwd = (long)getcwd(usercwd,128);

  if(strcmp(usercwd,pw->pw_dir)==0){

ret = sprintf(usercwd,”~”,NULL);

  }

  else if(strcmp(usercwd,”/”)!=0){

   ptmp1 = strrchr(usercwd,/);

sprintf(usercwd,”%s”,ptmp1+1);

  }

  if(strcmp(pw->pw_name,”root”)==0){

   sprintf(buf,”*[%s@%s %s]# “,

pw->pw_name,hostname,usercwd);

  }

  else{

   sprintf(buf,”*[%s@%s %s]$ “,

     pw->pw_name,hostname,usercwd);

  }

//command

  ssize_t g_ret,len;

char *line = NULL,*s_ret,*ptr=NULL;

  int con_cd=0;

  fprintf(stderr,”%s”,buf);

g_ret = getline(&line,&len,stdin);

  line[strlen(line)-1] = ;

  if(strcmp(line,”exit”)==0){

   exit(-1);

  }

  ptr = line;

  s_ret = line;

system(line);

  while(ptr!=NULL){

   s_ret = (char *)strsep(&ptr,” “);

   if(strcmp(s_ret,”cd”) == 0){

    con_cd=1;

    continue;

   }

else if(con_cd == 1){

    chdir(s_ret);

   }

  }

 }

 return 0;

}

//login function

int userlogin(struct passwd **pw)

{

char name[32],*passwd,*pret;

 struct spwd *sp;

 printf(“login:”);

 fflush(stdout);

 scanf(“%s”,name);

passwd = getpass(“password:”);

 sp = getspnam(name);

 if(sp == NULL){

  fprintf(stdout,”no is user![%s]n”,name);

return 0;

 }

 pret = crypt(passwd,sp->sp_pwdp);

 if(pret == NULL){

  fprintf(stdout,”crypt(%s)n”,name);

  return 0;

 }

if(strcmp(pret,sp->sp_pwdp) == 0){

  printf(“login successful!n”);

 }

 else{

fprintf(stdout,”passwd is error!n”);

  return 0;

 }

 *pw = getpwnam(name);

 if(*pw == NULL){

  printf(“getpwnam(%s) errorn”,name);

  return 0;

 }

return 1;

}