Strtok using dynamic memory - c

Question

I have the following code, and I need help getting and storing the last token. Right now the code tokenizes after every space, but when it gets to the end of my text file, it doesn't tokenize the last value. I'm pretty sure I need to have the token before the malloc statements, but when I add it in front, I get a seg fault. Does anybody know the issue? Initialized myStruct.extras = NULL above because of realloc; it is a char **.
token = strtok(fileArrayPTR[p],"X");
while (token!= NULL)
{
if (tempCounter == 0)
{
token = strtok(NULL," ");
myStruct.dimensions[1] = strtol(token,&ptr,10);
}else{
myStruct.extras = realloc(myStruct.extras,(extraCounter + 1) * sizeof(char *));
myStruct.extras[extraCounter] = malloc(strlen(token)+1);
strcpy(myStruct.extras[extraCounter],token);
token = strtok(NULL," ");
extraCounter++;
}
}
edit: forgot to put the incremented counter

Answer 1

This is (the second version of) the code from the question:
token = strtok(fileArrayPTR[p],"X");
while (token!= NULL)
{
if (tempCounter == 0)
{
token = strtok(NULL," ");
myStruct.dimensions[1] = strtol(token,&ptr,10);
}else{
myStruct.extras = realloc(myStruct.extras,(extraCounter + 1) * sizeof(char *));
myStruct.extras[extraCounter] = malloc(strlen(token)+1);
strcpy(myStruct.extras[extraCounter],token);
token = strtok(NULL," ");
extraCounter++;
}
}
This is not a self-contained program. We can improve it by:
Removing the structure.
Showing corresponding variable declarations.
Converting it into a simple main().
Those changes lead to:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
int extraCounter = 0;
char **extras = 0;
int tempCounter = 0;
char *ptr = 0;
char data[] = "10X16 something another-thing";
char *token = strtok(data, "X");
int dimension1 = strtol(token, &ptr, 10);
int dimension2 = -1;
while (token!= NULL)
{
if (tempCounter == 0)
{
token = strtok(NULL," ");
dimension2 = strtol(token, &ptr, 10);
tempCounter++;
}
else
{
extras = realloc(extras, (extraCounter + 1) * sizeof(char *));
extras[extraCounter] = malloc(strlen(token)+1);
strcpy(extras[extraCounter], token);
token = strtok(NULL, " ");
extraCounter++;
}
}
printf("Dimensions: %dx%d\n", dimension1, dimension2);
for (int i = 0; i < extraCounter; i++)
printf("%d: [[%s]]\n", i, extras[i]);
return 0;
}
And when run, it produces:
Dimensions: 10x16
0: [[16]]
1: [[something]]
2: [[another-thing]]
Is there a problem with that code? Yes, the code for the dimension2 doesn't reinvoke strtok(), so 16 is processed twice, once as a dimension and once as a string. Probably not what's wanted. Hence:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
int extraCounter = 0;
char **extras = 0;
int tempCounter = 0;
char *ptr = 0;
char data[] = "10X16 something another-thing";
char *token = strtok(data, "X");
int dimension1 = strtol(token, &ptr, 10);
int dimension2 = -1;
while (token != NULL)
{
if (tempCounter == 0)
{
token = strtok(NULL, " ");
dimension2 = strtol(token, &ptr, 10);
tempCounter++;
}
else
{
extras = realloc(extras, (extraCounter + 1) * sizeof(char *));
extras[extraCounter] = malloc(strlen(token) + 1);
strcpy(extras[extraCounter++], token);
}
token = strtok(NULL, " ");
}
printf("Dimensions: %dx%d\n", dimension1, dimension2);
for (int i = 0; i < extraCounter; i++)
printf("%d: [[%s]]\n", i, extras[i]);
return 0;
}
Compilation:
gcc -g -O3 -std=c11 -Wall -Wextra -Wmissing-prototypes -Wstrict-prototypes -Werror ss.c -o ss
Output:
Dimensions: 10x16
0: [[something]]
1: [[another-thing]]
Looks better...