How to pass a character string to a function in C - c

Question

I am trying to process a character string in order to change something in a file. I read from a file a character string which contains a command and an argument, separated by a space character. I separated this array in tokens.
Now I want to pass the second token, which is the argument to a function. My problem is that when I run my program, the screen freezes and nothing happens. Here is my separating way and the call to the function.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void create_file(char *argument)
{
//some code goes here
}
int main()
{
int i = -1;
char *token[5];
char command[20];
const char delim[1] = " ";
FILE *fin;
fin = fopen("mbr.op", "r");
while(fscanf(fin, "%[^\n]", command) == 1)
{
i = -1;
token[++i] = strtok(command, delim);
while(token[i] != NULL)
token[++i] = strtok(NULL, delim);
if(strcmp(token[0], "CREATE_FILE") == 0)
create_file(token[1]);
}
fclose(fin);
return 0;
}

Answer 1

You have a few errors, first command[20] is an uninitialised string and that will cause undefined behaviour. Second, you failed to check the first arg as well as the second, so I added a test where commented. Also, the strings are not long enough so I removed the length. Lastly I test for a NULL pointer passed to the function.
Edit code was added to the question to show that command[20] was initialised, but it is still too short to take the command and a reasonable file name (thanks to #ameyCU).
#include <stdio.h>
#include <string.h>
void create_file(char *argument)
{
if(argument == NULL)
printf("NULL pointer\n");
else
printf("Arg: %s\n", argument);
}
int main(void)
{
int i = -1;
char *token[5];
char command[] = "CREATE_FILE myfile.txt";
const char delim[] = " ";
token[++i] = strtok(command, delim);
while(token[i] != NULL)
token[++i] = strtok(NULL, delim);
if(token[0] != NULL && strcmp(token[0], "CREATE_FILE") == 0) // added test
create_file(token[1]);
return 0;
}
Program output
Arg: myfile.txt

Answer 2

The first error is present in array definition:
const char delim[1] = " ";
In C "" is a string - an array of characters delimited by '\0'. This means that what stands to the right of "=" is a string of two chars:
// ' ' + '\0'
//0x20 0x00
Therefore this should be an array of two chars:
const char delim[2] = " ";
or
const char delim[] = " ";