Appending values to a struct and printing it - c

Question

I have just started using structs and I am trying to append the variable names and its contents to the struct variables. For example.
INPUT:
PATH, getenv("PATH")
OUTPUT:
Var Name: PATH
Var Contents: /usr/sbin
This is my struct declaration
int var_counter = 0;
typedef struct ENV_VARIABLES
{
char var_name[MAX_VAR_NAME]; // Stored the Variable Name ie PATH
char var_content[MAX_SIZE]; // Stores the Variable Contents ie \home\bin\shell...
}env_variable;
env_variable *env_vars;
Here I am passing the parameters to the environVars() then printing them.
void iniEnvVars()
{
environVars("PATH", getenv("PATH"));
environVars("PROMPT", shellname);
environVars("CWD", getcwd("CWD", MAX_ARGS));
environVars("USER", getenv("USER"));
environVars("SHELL", "/home/.../");
environVars("TERMINAL", ttyname(STDIN_FILENO));
environVars("EXITCODE", EXITCODE);
printVars();
}
Here I am adding the contents to the struct.
int environVars(char *env_name, char *env_content)
{
// First we want to check if there are any stored items in the struct
// If there isnt, we store the first env_name and its contents;
// Else, we check if it is there, else we add it to the struct.
// If it is already there we modify its contents.
if(var_counter == 0)
{
var_counter++;
env_vars = calloc((size_t)var_counter, sizeof(env_variable));
strcpy(env_vars[var_counter].var_name, env_name);
strcpy(env_vars[var_counter].var_content, env_content);
}
else
{
for(int i = 0; i < var_counter; i++)
{
if(strcmp(env_name, env_vars[i].var_name) == 0)
{
printf("Found\n");
printf("Modifying Variable Contents\n");
strcpy(env_vars[i].var_content, env_content);
break;
}
else
{
var_counter++;
env_vars = realloc(env_vars,(var_counter)*sizeof(env_variable));
strcpy(env_vars[i].var_name, env_name);
strcpy(env_vars[i].var_content, env_content);
break;
}
}
}
return 1;
}
Here I am printing them.
void printVars()
{
if(var_counter == 0)
{
printf("There are no Enviromental Variables stored.\n");
}
else
{
for(int i = 0; i < var_counter; i++)
{
printf("Var Name: %s\n\n ", env_vars[i].var_name);
printf("Var Contents: %s\n\n ", env_vars[i].var_content);
}
}
}
I made use of calloc and realloc, but I am not quite sure if I were supposed to use malloc.
The error occuring is that it is not printing anything.
Ive did run a debug and the same thing happened. Nothing was printing.

Answer 1

Bug #1:
if(var_counter == 0)
{
var_counter++;
env_vars = calloc((size_t)var_counter, sizeof(env_variable));
strcpy(env_vars[var_counter].var_name, env_name);
strcpy(env_vars[var_counter].var_content, env_content);
}
What actually happen when var_counter is zero, is this:
var_counter = 1;
env_vars = calloc(1, sizeof(env_variable));
strcpy(env_vars[1].var_name, env_name);
strcpy(env_vars[1].var_content, env_content);
^
oh dear
You are writing outside the allocated memory
It should be:
strcpy(env_vars[0].var_name, env_name);
strcpy(env_vars[0].var_content, env_content);
Bug #2:
for(int i = 0; i < var_counter; i++)
{
if(strcmp(env_name, env_vars[i].var_name) == 0)
{
printf("Found\n");
printf("Modifying Variable Contents\n");
strcpy(env_vars[i].var_content, env_content);
break;
}
else
{
// YOU DON'T WANT THIS !!
var_counter++;
env_vars = realloc(env_vars,(var_counter)*sizeof(env_variable));
strcpy(env_vars[i].var_name, env_name);
strcpy(env_vars[i].var_content, env_content);
break;
}
}
The else makes reallocate and overwrite old entries again and again. You don't want that.
The code in the else should be after the loop. And only be executed in no match was found in the loop.