Need Help Fixing My C Program. Deals with File I/O

My program is supposed read in a file supplied from the commandline (filename.ext,) and write/overwrite out a file.

This file will be essentially the same as the original file, but will have all characters on all lines the reverse of the original. For example:
The original file has:
Jack Spratt
could eat no fat.

The output file will look like:

ttartpS kcaJ
.taf on tae dluoc


The approach i decided to take was to read the input file, creat a temporary file, and then reverse it there, later toss the reverse d strings into the output file, but somehow its not working, i believe it has something to do with my reverse function, can anyone help fix it? I also get these errors:

C:\Documents and Settings\Administrator\My Documents\100_php_scripts\myown.c In function `main':

28 C:\Documents and Settings\Administrator\My Documents\100_php_scripts\myown.c [Warning] passing arg 1 of `reverse' makes pointer from integer without a cast
here are the codes i have!

Code:

#include <stdio.h>


void reverse( char *sPtr ); // function to revers the characters from input to output

int main (void)
{
    FILE *fileinput; //pointer to file being modified
    FILE *temp;//temporary file pointer
    FILE *fileoutput;//pointer to where contents will be written
    int c;//hold characters from input file
    char filename [30]; //file name create char array
    
    printf("This program reverses your text file.\n");
    printf("Enter a File to be modified:\n" );
    scanf("%29s",filename);
    
    //opens input file
    if ((fileinput = fopen (filename, "r")) != NULL){ 

       //creates temporary file
       if ((temp = tmpfile()) != NULL) {
          printf("\nThe File before modification is:\n");
          
             //read characters from file and place in temporary file
             while((c= getc(fileinput)) != EOF) {
                putchar (c);
                (temp,reverse(c)); 
                 }//end while
                
                rewind (temp);
                rewind(fileinput);
                
                printf("\n\n The File after modification i:\n");
                
                //read from temporary file and write to output file
                while ((c = getc(temp)) != EOF) {
                   putchar(c);
                   putc(c,fileoutput);
                   }// end while
                   
                   }//end if
                   
                   else{ // if temporary file could not be opened
                      printf("unable to open temporary file\n");
                      }//end else
                      
                           }           //end if

                else {//if input file could not be opened
                     printf("Unable to open %s\n",filename);
                }//end else
                
    fclose (fileoutput);            
    fclose(fileinput);
    fclose(temp);
   
    return 0;
}
                
void reverse(char * sPtr ) // reverse function
{
   if( sPtr[ 0 ] == '\0' ){
      return;
   }
      else{
         reverse( &sPtr[ 1 ] );

         putchar( sPtr[ 0 ] );
     }
} // end function

 

Generally, if you want to cast something, just do (int)variableName iirc.