File handling in C: Strip spaces at the beginning and end of text file

Question

The following is a function that reads a file user.dat (attached after the code) and extracts a string and an int value delimited by ", " and "\\n" respectively.

void getUsers()
{
     int i, t;
     char *token1, *u;
     FILE *fu = fopen("user.dat", "r");
     const char s[2] = ", ";
     if(fu != NULL)
     {
        char line1[20];
         while(fgets(line1, sizeof line1, fu) != NULL)
         {
             token1 = strtok(line1, s);
             for(i=0;i<2;i++)
             {
                 if(i==0)
                 {  
                     u = token1;
                     token1 = strtok(NULL,s);
                 } else {
                     t=atoi(token1);
                 }      
             }
             addOuterNode(u,t);
         }
         printOuterNode();
         fclose(fu);
     } else {
         perror("user.dat");
     }
}

The user.dat file is as follows:

1000, 76
0095, 81
2910, 178
0001, 1
<EOF>

The program works fine if the above format is maintained.

However I run into problems (SIGSEGV generally as the *u and t values are sent to a function that inserts them into void * data elements in nodes of a linked list/nested linked list) when there are stray spaces or newlines in the file. Eg:

<newline>
1000, 76
 <space>
0095, 81
2910, 178
0001, 1
 <space><newline>
<newline>
<EOF>

Would you be able to help me to preprocess the user.dat textfile so that I can remove the unwanted whitespace characters?

Answer 1

You can preprocess a file to exclude lines containing only whitespace characters. Eg in Perl this would be: perl -ne "print if !/^\\s*$/" input.txt > output.txt