fgets giving me a segfault when passing only spaces - c

Question

I am trying to make a shell and one of the conditions i am looking out for is when the user enters a bunch of spaces. However, I get a segfault from fgets when I input any number of spaces in the terminal. It can be one space, or it can be a whole bunch of them followed by a random character. I keep getting a segfault.
Development:
I noticed that I don't get a segfault when I remove my tokenize function. Why would this be the case?
Here's my code:
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include <stdio.h>
/* Initialize variables and methods */
int status;
int i;
int one_nonspace = -1;
int on = 1;
char input[101];
char temp[101];
char* tokenized;
char operators[3] = {'>', '<', '|'};
char** tokens;
void getInput(char *prmpt, char *buff){
printf(">:");
fgets(buff, 101, stdin); //segfault here when input spaces.
/*printf("works!");*/
if(one_nonspace != -1){
printf("spaces");
memcpy( temp, &buff[i], (101-i) );
temp[100] = '\0';
}
if(buff[strlen(buff) -1] != '\n'){
int over = 0;
while(fgetc(stdin) != '\n')
over++;
if(over>0)
{
printf("Command is over 100 characters. Please try again\n");
status = 1;
}
}
else{
buff[strlen(buff) - 1] = '\0';
status = 0;
}
}
char** tokenize(char* a_str)
{
char** result = 0;
size_t count = 0;
char* tmp = a_str;
char* last = 0;
char delim[2];
delim[0] = ' ';
delim[1] = 0;
/* Count how many elements will be extracted. */
while (*tmp)
{
if (' ' == *tmp)
{
count++;
last = tmp;
}
tmp++;
}
/* Add space for trailing token. */
count += last < (a_str + strlen(a_str) - 1);
/* Add space for terminating null string so caller
knows where the list of returned strings ends. */
count++;
result = malloc(sizeof(char*) * count);
if (result)
{
size_t idx = 0;
char* token = strtok(a_str, delim);
while (token)
{
assert(idx < count);
*(result + idx++) = strdup(token);
token = strtok(0, delim);
}
assert(idx == count - 1);
*(result + idx) = 0;
}
return result;
}
/* Create a parser Feb 2*/
int main(int argc, char **argv){
while(on){
getInput(">: ", input);
tokenized = input;
if(status == 0){
/*printf("%s\n", input);*/
}
/*Split the line into tokens*/
if(input[0] != ' ')
tokens = tokenize(tokenized);
/*if tokens[0] == 'exit', then quit.
*/
if(strcmp(*(tokens),"exit") == 0){
break;}
/*2/3 Now we need to do something with the split up tokens*/
/*printf("input after token: %s\n", input);*/
/*Free the tokens at the end!!! Remember this!*/
if (tokens)
{
int i;
for (i = 0; *(tokens + i); i++)
{
printf("%s\n", *(tokens + i));
free(*(tokens + i));
}
free(tokens);
}
}
return 0;
}

Answer 1

Here's the problem:
/*Split the line into tokens*/
if(input[0] != ' ')
tokens = tokenize(tokenized);
/*if tokens[0] == 'exit', then quit.
*/
if(strcmp(*(tokens),"exit") == 0){
break;}
When input begins with a space character, you skip the tokenize function and attempt to dereference tokens - a NULL pointer.
Edit: you are trying to debug with print statements and that is a valid method, but remember to flush the buffers or you won't get an accurate idea of where the problem is if the crash happens before there's any output. You can flush them explicitly with fflush or simply use newline characters if you're on a terminal, as they are usually line buffered.