Thread: Problem with passing variables between functions

Code:

#include <stdio.h>
#include <string.h>


const char *seperationChar = "@";


void getUsername(char *usernamestring)
{
	char *c = usernamestring;
	int i = 0;
	int sep = 0;
	while(*c)
	{
		if(strchr(seperationChar, *c))
		{
			printf("%d", i);
			sep = i;
		}
		i++;
		c++;
	}

	char username[11];

	int j;

	for(j = 0; j< sep; j++)
	{
		username[j] = usernamestring[j];
	}
	
	usernamestring = username;
}

void registerUser(char *usernamestring)
{


	FILE *logon_file;
	logon_file = fopen("users.txt", "a");
	fprintf(logon_file, "%s", usernamestring);
	fclose(logon_file);

}

int main()
{
	char name[11] = "martin@1234";
	getUsername(name);
	printf("\n%s\n", name);
	return 0;
}

The code is supposed to take a string formatted as "name@password" and return the name part.

I've run this through the debugger and usernamestring at the end of the getUsername() function is set to the correct value. However, when it returns to main the variable reverts to it's original value.

I thought the changes would be applied to the original as I passed it to the function as a pointer.

Any help appreciated.

I think you should declare username variable first in main() and then pass it to getUsername()
as a second arg, and then deal with it in that method, rather than making a new one and then
setting it to username...

Code:

void getUsername(char *usernamestring, char * username)
{
	char *c = usernamestring;
	int i = 0;
	int sep = 0;
	while(*c)
	{
		if(strchr(seperationChar, *c))
		{
			printf("%d", i);
			sep = i;
		}
		i++;
		c++;
	}


	int j;

	for(j = 0; j< sep; j++)
	{
		username[j] = usernamestring[j];
	}
	
	
}

Code:

int main()
{
	char name[11] = "martin@1234";
	char username[11]="";
	getUsername(name, username);
	printf("\n%s\n", username);
	return 0;
}

Code:

int main(void)
{
	char user[50] = "testuser@123456";
	char userTwo[50] = "jabman@999";
	printf("\n\nUser string created");
	registerUser(user);
	printf("\n\nUser registered");
	
	printf("\n\nget username");
	char uname[50];
	getUsername(user, uname);
	printf("\n\nThe returned user name was : %s ", &uname);
	strcat(uname, "@");
	printf("\n\nThe returned user name is now : %s ", &uname);
	if(searchForUser(uname)==1)
	{
		printf("\n\ntrue User %s found", user);
	}
	else
	{
		printf("\n\nfail real user find");
	}
	
	
	printf("\n\nTry and get password");
	char pass[50];
	getPassword(uname, pass);
	printf("\n\nThe returned password was : %s \n\n", pass);
	
}

Code:

...
void getPassword(char *username, char *password)
{
	FILE *logon_file;
	logon_file = fopen("users.txt", "r+a");
	char tmp[100];
	int userLength = strlen(username);
	char tempPassword[50];
	
	
	while(fgets(tmp, 100, logon_file))
	{	
		
		if(strstr(tmp, username))
		{
			tempPassword = &tmp;
			int i; 
			for(i = 0; i<userLength; i++)
			{
				tempPassword++;
				password = tempPassword;
			}
		}
		
	}
	fclose(logon_file);
}
....

I get:

The returned password was : ��



The problem is in the getPassword function shown above.

Basically, I have a txt file (users.txt) containing passwords and user names
One username/password combo per line
Each username seperated from its password with a '@' symbol

The function should take a username, find the line containing that name
e.g.
"thisIsTheNameIWanted@password"

It should then advance the pointer on the above string by the length of the username string and result in the password parameter being set to the password portion only.

Sorry if this doesnt make sense. I wrote a detailed description then my connection was lost and I've had to redo quickly. I will be happy to clarify anything.

Again, I appreciate all the help this forum gives me.

but then why do you need getUserName() method?
as i understand your input is username and you need to look for his password in .txt file, is that right?

Originally Posted by r00t

but then why do you need getUserName() method?
as i understand your input is username and you need to look for his password in .txt file, is that right?

It is a client/server environment. The way I have it setup is that the server is passed a whole "logon" string including username and pasword. From that I need to getUsername to check if the user exits, then if it does i want to get the password

MK27, once again you come to my rescue. It is really appreciated.

Not sure if it's just me but the site availability seems bad tonight. Keep getting a database error returned.

Thanks for the reply.

Code:

void getPassword(char *username, char *password)
{
	FILE *logon_file;
	logon_file = fopen("users.txt", "r+a");
	char tmp[50];
	int userLength = strlen(username);

	while(fgets(tmp, 50, logon_file))
	{	
		if(strstr(tmp, username))
		{
			int i; 
			for(i = 0; i<userLength; i++)
			{
				tmp++;   <-----  lvalue required as increment operand

				strcopy(password, tmp);
			}
		}
		
	}
	fclose(logon_file);
}

I made a few changes but it won't compile. I get the above error. It really is these pointers etc that are my stumbling block. I'm still having to code java at the same time and have coded java for quite a bit so its making it a little more difficult.

Thanks again.

thankyou. i think your 100% correct. I dont need the for loop do i. Il try this as soon as am back at comp. Am on phone at the minute.