Thread: Some very strange behaviour with argv

For some reason, using <string.h> functions on argv[1] messes up the values in my global arrays.

Here is a shortened version of my code:

Code:

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

char* username[50];
char* password[50];
char* type[50];
int recordcount;

/*...
some functions
...*/

int main(int argc, char* argv[])
{
	getData(); //Reads some file and stores stuff into the 3 global string arrays

	if (argc == 1)
		syntaxerror(); //Checks there is at least one extra parameter when calling the program

	if (strcmp("-menu",argv[1]) == 0) //Calls menu() if the 1st parameter is -menu
		menu();
	else
	{
		/* Rest of program */

So for example when I tested the program, username[0] is what it's supposed to be until it hits the line:
if (strcmp("-menu", argv[1]) == 0).
Then, username[0] changes its value completely.
menu() was never called when testing.

I tested it even further and when just doing a strcmp("menu", argv[1]); by itself, it did not change username[0]. However, it did when putting it in an if statement and comparing it to 0.

I cannot think of any reason why it would do this...

They are global because many of the functions need to access them, and it's more convenient than passing them as parameters.

Alright here's the program (modified for testing) everything that runs up to the point of where it messes up

Code:

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

char* username[50];
char* password[50];
char* type[50];
int recordcount;

//Gets all the data for the 3 arrays containing usernames, passwords, and types

int getData()
{
	FILE* pfile;
	pfile = fopen("password.csv", "a+");

	char * token;
	char line[300];
	int i = 0;

	while (fgets(line, 300, pfile) != NULL)
	{
		printf("Getting the line: %s", line);
		token = strtok(line,",");
		printf("Token 1 stored in username[%d]: %s\n", i, token);
		username[i] = token;
		token = strtok(NULL,",");
		printf("Token 2 stored in password[%d]: %s\n", i, token);
		password[i] = token;
		token = strtok(NULL,"\n");
		printf("Token 3 stored in type[%d]: %s\n", i, token);
		type[i] = token;
		i++;	
	}
	recordcount = i;
	return 0;
}

int main(int argc, char* argv[])
{	
	getData();

	//Checks that there aren't no parameters
	if (argc == 1)
		syntaxerror();

	printf("Test 0: %s, %s, %s\n", username[0], password[0], type[0]);

	char * switchParameter = argv[1];
	printf("Test 1: %s, %s, %s\n", username[0], password[0], type[0]);

	if (strcmp("-menu",switchParameter) == 0)
		menu();
	else
	{
		printf("Test 2: %s, %s, %s\n", username[0], password[0], type[0]);

		/*Rest of program*/
	}
}

This is tested using a password.csv file with just the single line:

Code:

abc,def,ghi

running ./a.out [somerandomparameter not -menu]
and the output up to this point is:

Code:

Getting line: abc,def,ghi
Token 1 stored in username[0]: abc
Token 2 stored in password[0]: def
Token 3 stored in type[0]: ghi
Test 0: abc, def, ghi
Test 1: abc, def, ghi
Test 2: �W�, , 8��

Now as you can see... Test 2 is completely messed up and I have no idea why.
Thanks in advance guys, really appreciate it.

ahhh yes I see now, thanks!
To fix it, I just replaced the things with username[i] = strdup(token);