Getting words from text file to an array

Question

My text file is formated like that:

my.txt
Red
Green
Blue
Yellow

I\'m tring to get words like that:

typedef char * string;
         


        

Answer 1

You'll need to allocate memory for your null-terminated strings.

At the moment you are only allocating memory for 4 char *, but these pointers are uninitialized and therefor will result in UB (undefined behavior) when you try to write data to the memory pointed to by them.

---

Working example snippet

The use of "%127s" in the below snippet is to prevent us writing outside the bounds of the allocated memory. With the format-string in question we will at the most read/write 127 bytes + the null-terminator.

Please remember that further error checks should be implemented if this is to be used in "real life".

• Check to see that file_handle is indeed valid after attempt to open the file
• Check to see that malloc did indeed allocate requested memory
• Check to see that fscanf read the desired input

---

#include 
#include 
#include 

int
main (int argc, char *argv[])
{
  int i;
  char * lines[4];
  FILE *file_handle = fopen ("my.txt", "r");

  for (i =0; i < 4; ++i) {
    lines[i] = malloc (128); /* allocate a memory slot of 128 chars */
    fscanf (file_handle, "%127s", lines[i]);
  }

  for (i =0; i < 4; ++i)
    printf ("%d: %s\n", i, lines[i]);

  for (i =0; i < 4; ++i)
    free (lines[i]); /* remember to deallocated the memory allocated */

  return 0;
}

output

0: Red
1: Green
2: Blue
3: Yellow