字符串参数变空 [英] string parametres becoming empty
问题描述
我正在尝试这样做：
#include< stdlib.h>
#include< stdio.h>
#define FILE" / tmp / myfile"
#define USERS_LIST" / tmp / userslist"
int main（）{
//打开文件
FILE * fp = fopen（FILE，" r"）;
char buf [512];
fgets（buf，sizeof（buf），fp）;
char * username，* password，* pid ;
pid = strtok（buf，" ;;"）;
username = strtok（NULL，" ;;"）;
password = strtok（NULL;" ;;"）;
if（SearchUser（username）！= NULL）{
printf（" user exists"）;
}
else {
if（RegisterUser（用户名，密码）== 0）{
printf（ 注册成功）;
}
}
}
/ *搜索名称为<的用户;用户名> ;.
返回< password>如果找到用户。
如果找不到具有给定用户名的用户，则返回NULL。* /
char * SearchUser（char * username）{
FILE * fp = fopen（USERS_LIST，" r"）;
while（feof（fp）== 0）{
char line [100 ];
char * buf = fgets（line，sizeof（line），fp）;
char * iUsername = strtok（buf，" ;;"）;
char * iPassword = strtok（NULL，" ;;"）;
if（strcmp（iUsername，username）== 0）{
fclose（fp）;
返回iPassword;
}
}
fclose（fp ）;
返回NULL;
}
/ *使用给定的< username>注册用户和<密码>。
如果注册成功，则返回0。
如果注册失败，则返回-1。* /
int RegisterUser（char *用户名，字符*密码）{
FILE * fp = fopen（USERS_LIST，" a"）;
if（fprintf（fp，"％） s;％s; \ n"，用户名，密码）< 0）{
fclose（fp）;
返回-1;
}
fclose（fp）;
返回0;
}
但是当我在SearchUser和RegisterUser函数中查看gdb我需要注意我传递的字符串参数是空的...不是NULL，（但是
例如而不是< username> ;是erik它是"
....而在RegisterUser中，当我打开文件时，有些东西已被写入了b
但它是无稽之谈（比如< username = erik password = mypwd，
我找到的文件/（）/£GY;（）"（G（））....我无法理解
存在问题......
非常感谢
Erik写道：我是试图这样做：
#include< stdlib.h>
#include< stdio.h>
＃define FILE" / tmp / myfile" ;
你确定要这么做????
-
Ian Collins。
是的，为什么？ FILE定义将消失，因为我会询问用户
文件名，但是现在它就像那样......
Erik写道：是的，为什么？ FILE定义将消失，因为我会询问用户
文件名，但现在它就像那样...
你有#define FILE" something ;
再向下你有
FILE * fp = fopen（FILE，r）;
想想看什么在那里发生了第一个FILE
令牌，你发布的代码不能编译。
你的代码也缺乏错误处理。
Hi, i''m trying to do this :
#include <stdlib.h>
#include <stdio.h>
#define FILE "/tmp/myfile"
#define USERS_LIST "/tmp/userslist"
int main() {
//open file
FILE *fp = fopen(FILE, "r");
char buf[512];
fgets(buf, sizeof(buf), fp);
char *username, *password, *pid;
pid = strtok(buf, ";");
username = strtok(NULL, ";");
password = strtok(NULL; ";");
if (SearchUser(username) != NULL) {
printf("user exists");
}
else {
if (RegisterUser(username, password) == 0) {
printf("registration successful");
}
}
}
/* Searches for user with name <username>.
Returns <password> if user is found.
Return NULL if no user with given username is found.*/
char *SearchUser(char *username) {
FILE *fp = fopen(USERS_LIST,"r");
while (feof(fp) == 0) {
char line[100];
char *buf = fgets(line, sizeof(line), fp);
char *iUsername = strtok(buf, ";");
char *iPassword = strtok(NULL, ";");
if (strcmp(iUsername, username) == 0) {
fclose(fp);
return iPassword;
}
}
fclose(fp);
return NULL;
}
/* Registers user with given <username> and <password>.
Returns 0 if registration successful.
Return -1 if registration failed.*/
int RegisterUser(char *username, char *password) {
FILE *fp = fopen(USERS_LIST, "a");
if ( fprintf(fp, "%s;%s;\n", username, password) < 0) {
fclose(fp);
return -1;
}
fclose(fp);
return 0;
}
But when I look with gdb inside SearchUser and RegisterUser functions I
notice that the string parameters I passed are empty... not NULL, (but
for example instead of <username> being "erik" it is "")
.... and in RegisterUser when I open the file, something has been
written but it is nonsense( like <username=erik password = mypwd,
inside the file i found /()/￡GY;()"(G() ) .... I can''t understand
where resides the problem...
thank you very much
Erik wrote:Hi, i''m trying to do this :
#include <stdlib.h>
#include <stdio.h>
#define FILE "/tmp/myfile"
Are you sure you want to do that????
--
Ian Collins.
yes, why ? the FILE define will disappear, as I will ask user for
filename, but for now it''s like that...
Erik wrote:yes, why ? the FILE define will disappear, as I will ask user for
filename, but for now it''s like that...
You have #define FILE "something"
Further down you have
FILE *fp = fopen(FILE, "r");
Think about what happens with the first FILE
token there, your code as posted does not compile.
Your code also lack error handling all over.
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