Simple C program to create dictionary for mobile phones.

sk8harddiefast

sk8harddiefast

Sometimes the dictionary we use (for any purpose) is not doing the job. This is a simple dictionary I wrote in C that creates all mobile phone numbers in Greece. In Greece phone numbers are 10 numbers and start from 69. Example: 697 0000 000. You can use it to for you country just changing for if you have more or fewer than 10 numbers and fprintf if your phones does not start from 69 :D

Code: 
#include <stdio.h>

main ()
{
int i;
FILE *file;
	file = fopen ("dictnum0", "w");
	for (i=00000000; i<100000000; i++)
	{
		fprintf (file, "69%08d\n", i);
		}
fclose(file);
}
 
Not to rain on your parade, but there must be a hundred ways to do this on the cmdline already.

One of the lesser known is probably jot(1)()

Code: 
jot 10000000 6900000000
 
Enjoy learning C :)

Note you don't need to use any 0-paddings when initializing i and setting a range. Speaking of range, don't forget that some systems use int sizeof 2 bytes, so way out of your range.

Also some checks on fopen are in order.
 
More importantly any function that is not of type void *should* use return to leave (i.e. your main that is of type int lacks a return statement), and also symbol type implication has been removed by C99, so you _must_ declare main's return type.
 
This is a template that I use for all standalone C programs;

Code: 
#include<stdio.h>
#include<stdlib.h>

int main(int argc, char **argv)
{
    return EXIT_SUCCESS;
}

If you're beginning with C, it's best to type this out of your head, before programming anything that requires main().
 
Here is a 5-minutes imrpvoeprovement: the program accepts the prefix from the command line or uses the fixed 69 value. Moreover it builds a format string with the computed padding (not a fixed 8) depending on the length of the prefix. It can be improved much more considering other arguments (e.g., the filename, the number of digits, the number of numbers....).

Code: 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main ( int argc, char** argv)
{
  int i;
  char* prefix;
  int prefix_length = 2, max_length = 10;
  int padding = 8;
  int max_numbers = 100000000;
  char* format_string;


  // get the prefix from the command line or from a fixed value
  if( argc > 1 ){
    printf("\nUsing prefix from command line :%s", argv[1] );
    prefix = argv[1];
  }
  else{
    prefix = "69";
    printf("\nUsing builtin prefix %s", prefix);
    
  }

  // get the prefix length
  prefix_length = strlen( prefix );
  // compute the padding
  padding = max_length - prefix_length;
  printf("\nPrefix is %d digits, max length is %d and padding is %d digits\n", prefix_length, max_length, padding);

  // the format string will be <prefix>%0<padding>d
  format_string = malloc( sizeof(char) * (prefix_length + 2 + 1 + 1 + 1 + 1 ) );
  sprintf( format_string, "%s%%0%dd\n", prefix, padding );
  printf("\nFormat string is [ %s ]", format_string );
  


  FILE *file;
  file = fopen ("dictnum0", "w");
  for (i=0; i < max_numbers; i++)
    {
      fprintf ( file, format_string , i);
    }
  fclose(file);

  return 0;
}
 
If you are just dumping data to a file in a sequence it's faster to use direct I/O instead of buffered one to avoid data duplication in your memory since all modern filesystems will cache the writes to memory anyways.
 
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