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【C】实现用户登录，系统命令的实现

作者:黄弘玄 / 发布于2013/10/11/ 658


	#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 '$'
	//and the current work path is truncated from the last '/' to the end
	 ret_cwd = (long)getcwd(usercwd,128);
	 if(strcmp(usercwd,pw->pw_dir)==0){
	 ret = sprintf(usercwd,"~\0",NULL);
	 }
	 else if(strcmp(usercwd,"/")!=0){
	 ptmp1 = strrchr(usercwd,'/');
	 sprintf(usercwd,"%s",ptmp1+1);
	 }
	 if(strcmp(pw->pw_name,"root")==0){
	 sprintf(buf,"*[%s@%s %s]# ",
	 pw->pw_name,hostname,usercwd);
	 }
	 else{
	 sprintf(buf,"*[%s@%s %s]$ ",
	 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] = '\0';
	 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) error\n",name);
	 return 0;
	}

	return 1;

	}

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