Seg fault when printing array after passing to function, please explain behaviour - c

Question

So i am attempting to pass a string array (char** arguments) to a function, fill the array with values and then print those values after returning from the function. The problem occurs when I try to print the first value of "arguments" which gives me a segmentation fault. Why is this? when I print the values in the "getArguments" function all goes as expected. I am new to C and yes this is an assignment. I am not looking for you to write this code for me however I would like an explanation of this behaviour as I try to understand this concept.
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#define BUFFERSIZE 81
int getArguments(char** arguments, char* argument);
void getPath(char* pathBuffer);
int checkForDirectoryChange(char **arguments, int num_args);
int main(int argc, char *argv[]){
char * command;
char ** arguments = NULL;
char * cd_path;
int len, pid, ret_code, cd_requested = 1;
char buffer[BUFFERSIZE];
/* Get user input and the first token */
printf("Enter a command: > ");
command = fgets(buffer,BUFFERSIZE,stdin);
printf("The command entered was %s",buffer);
len = strlen(buffer);
if(buffer[len-1] == '\n')
buffer[len-1]='\0';
cd_requested = getArguments(arguments, command);
printf("The argument passed is now: %s\n", arguments[0]);
if(cd_requested == 0){
fprintf(stdout,"Change directory requested.\n");
}
/*
char * pathBuf;
getPath(pathBuf);
free the memory allocated */
/*
pid = fork();
if(pid){
wait(NULL);
}else{
ret_code = execvp(*arguments, arguments);
if(ret_code){
printf("The fork failed, exiting.");
exit(0);
}
}*/
}
int getArguments(char** arguments, char* command){
int n_spaces = 0,i;
char *token;
token = strtok(command, " ");
/* Loop until we have gotten all of the tokens */
while (token) {
arguments = realloc (arguments, sizeof (char*) * ++n_spaces);
if (arguments == NULL){
printf("Memory allocation failed: token - %d\n", n_spaces);
exit (-1); /* memory allocation failed */
}
arguments[n_spaces-1] = token;
token = strtok (NULL, " ");
}
/* realloc one extra element for the last NULL */
arguments = realloc (arguments, sizeof (char*) * (n_spaces+1));
arguments[n_spaces] = 0;
/* print the result */
for (i = 0; i < (n_spaces+1); ++i)
printf ("arguments[%d] = %s\n", i, arguments[i]);
return strcmp("cd",arguments[0]);
}
int checkForDirectoryChange(char** arguments, int num_args){
return 0;
}
void getPath(char* pathBuffer){
size_t n;
n = confstr(_CS_PATH, NULL, (size_t) 0);
pathBuffer = malloc(n);
if (pathBuffer == NULL)
abort();
confstr(_CS_PATH, pathBuffer, n);
}

Answer 1

It is because getArguments() only reassigned the copy of pointer to pointer of characters inside itself. arguments in main() was not updated.
You should define getArguments() as
int getArguments(char*** arguments, char* command) {
/* ... */
while (token) {
*arguments = realloc (*arguments, sizeof (char*) * ++n_spaces);
if (*arguments == NULL){
printf("Memory allocation failed: token - %d\n", n_spaces);
exit (-1); /* memory allocation failed */
}
(*arguments)[n_spaces-1] = token;
token = strtok (NULL, " ");
}
/* ... */
}
And call it as the following inside main().
cd_requested = getArguments(&arguments, command);