Hi Guys,

Can someone give me a simple example of how to read a file of userids and passwords such as a file called passwords containing:

a001mm password1
cd98fk outwilldo
lmn99p abc123456

into an array of strings in c. I know they need to be arrays of arrays of chars but not sure how to put this altogether.

if you could knock up a small prog that reads the above file into arrays of userid and password respectively then uses a for loop to fprint the contents of one of the arrays out, that would be excellent.

thanks in advance

Justice comes to he who waits

How about if I knock up a small program that reads the file into one array then outputs the contents to the screen using a do while loop??

Be sure to come back and let us know if our suggestions helped!

Yeah, that would be helpfull cheers.

Justice comes to he who waits

So you know what i have upto now:

a passwords.txt file with userids followed by a space then the passwords in the following format:

user0001 password01
user0002 password02
user0003 password03

#include <stdio.h>
#include <strings.h>

char *id[3];
char *pw[3];

int main(void)
{
FILE *pwdFile = fopen("passwords.txt", "r");
while(fscanf(pwdFile, "%s%s", id, pw) !EOF)
{
;/* want some way of incrementing id & pw as wont let me id++, pw++ in above fscanf */
}

printf("%s %s\n", id, pw);
/* this prints out last item in file ok
but i obviously want to print them all
*/

/* this next bit causes segment error */
int count;
for(count = 0; count < 3; count++)
{
printf("%s %s\n", id[count], pw[count]);
}
return 0;
}

Justice comes to he who waits

The problem is you are declaring an array of character pointers, but you aren't initializing them to anything. I created a structure and made sure the user and password strings are larger than anything in passwords.txt:

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <stdio.h>

struct demo_struct
{
char id[10];
char pw[20];
};

int main(int argc, char *argv[])
{
FILE *fp;
char retstr[BUFSIZ];
char *f1, *f2, *p;
int max_cnt=5;
int i, cnt=0;

struct demo_struct usr[5];

if ((fp=fopen("passwords.txt", "r")) == NULL)
{
printf("ERROR: can not open passwords.txt file:\n");
exit(1);
}

while (fgets (retstr, BUFSIZ, fp) != NULL)
{
if ((p = strchr(retstr, '\n')) != NULL)
*p = '\0';
if(cnt == max_cnt)
break;

f1=strtok(retstr, " ");
f2=strtok(NULL, " ");
strcpy(usr[cnt].id, f1);
strcpy(usr[cnt].pw, f2);
cnt++;
}

for(i=0; i < cnt; i++)
printf("%s %s\n", usr[i].id, usr[i].pw);

fclose(fp);
exit(0);
}

Thanks for the reply.

It looks a bit more complicated than what i was trying but then again mine doesnt work :-)

I have typed in your code above but when i complile it with gcc i get to warnings about incompatible implicit declaration of built-in function exit.

It still compiles and does read in the file and print it out fine however but i was wondering how to get shot of the warnings?

cheers

Justice comes to he who waits

You're welcome. Interesting problem. I originally created that code on a Solaris 7 box. I moved it over to an old Red Hat 7.1 system using gcc:

Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.1 2.96-81)

I didn't have any problems.

What happens if you replace the exit with the return?