/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

This program shifts x, y, z co-ordinates of any system based on
the value of dx, dy, dz and writes the new set of (x,y,z) in a new
file. 

INPUT :

Input file must have the name 'shift-xyz-input.xyz' and (x,y,z) 
co-ordinates must be in the following format (space or tab separated)

First Line   : Number of atoms, N
Next N Lines : x, y, z of each atom

DESCRIPTION OF VARIABLES :

Nbuf     First line of the input file, stored as string
Abuf     Atomic Number of the atom, stored as string
xbuf     x co-ordinate of the atom, stored as string
ybuf     y co-ordinate of the atom, stored as string
zbuf     z co-ordinate of the atom, stored as string

N        Nbuf converted to integer, using atoi()
         Number of atoms

Atom[i]  Abuf converted to integer, using atoi()
         One dimensional array for atomic number of N atoms  

x[i]     xbuf converted to double precision number, using atof()
         One dimensional array for storing x co-ordinate of N atoms  

y[i]     ybuf converted to double precision number, using atof()
         One dimensional array for storing y co-ordinate of N atoms   

z[i]     zbuf converted to double precision number, using atof()
         One dimensional array for storing z co-ordinate of N atoms


COMPILATION/EXECUTION PROCEDURE :

gcc -o shift-xyz.x shift-xyz.c -lm
./shift-xyz.x


OUTPUT :

If the compilation and execution is successful, the program writes an output 
file named in 'shift-xyz-ouput.xyz' format with shifted (x,y,z) co-ordinates

First written : Gowtham, Thu Dec 22 19:32:02 EST 2005
Last modified : Gowtham, Thu Dec 22 21:22:51 EST 2005

For comments and/or suggestions, please contact mail@sgowtham.net

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>

main() 
{

/* Defines input and output files */
  FILE *input;
  FILE *output;

/* Declaration and initialization of variables */
  char   Nbuf[100]={'\0'};
  char   Abuf[100]={'\0'};
  char   xbuf[100]={'\0'};
  char   ybuf[100]={'\0'};
  char   zbuf[100]={'\0'};

  int      Atom[100]={0};
  double   x[100]={0};
  double   y[100]={0};
  double   z[100]={0};

  int     i, N;
  double  dx, dy, dz;
  
  dx=0.500;  /* Change this value to indicate dx */
  dy=0.500;  /* Change this value to indicate dy */
  dz=0.500;  /* Change this value to indicate dz */

/* Opens the input file for reading */
  input = fopen("shift-xyz-input.xyz", "r");

  if (input == NULL) {
    printf("\nInput File empty or corrupted! Exiting...\n");
    exit (1);
  }

/* Creates the output file and opens it for writing */
  output = fopen("shift-xyz-ouput.xyz", "w");

/* Reads the first line of the input file and stores it as N */
  fscanf(input, "%s", Nbuf); 
  N = atoi(Nbuf);

/* Reads and stores the (x, y, z) for each atom, first as a string (buffer) 
  and later stores it as an array element using appropriate conversion 
  mechanism */
  for(i=0; i<N; i++) {
    fscanf(input, "%s", Abuf);
    Atom[i]= atoi(Abuf);
  
    fscanf(input, "%s", xbuf);
    x[i]= atof(xbuf);
  
    fscanf(input, "%s", ybuf);
    y[i]= atof(ybuf);
  
    fscanf(input, "%s", zbuf);
    z[i]= atof(zbuf);
  }

/* Calculates the new x and y co-odrinates of atoms based on the value of
  dx, dy and dz */
  for(i=0; i<N; i++)  {
    x[i] = x[i] + dx;
    y[i] = y[i] + dy;
    z[i] = z[i] + dz;
  }

/* Final values are written in the output file */
  fprintf(output, "%d\n", N);

  for(i=0; i<N; i++){
    fprintf(output, "%d",       Atom[i]); 
    fprintf(output, "\t%lf",    x[i]);
    fprintf(output, "\t%lf",    y[i]);
    fprintf(output, "\t%lf\n",  z[i]);
  }

/* Closes the input and output files */
  fclose(input);
  fclose(output);

/* Confirmation to the user */
  printf("Please open shift-xyz-output.xyz for results\n\n");

/* Program Ends */
}