[os] v2 systems calls - Covert file 1 to file 2 inverting upper/lower cases

[xgiovio]

/*
 *
 *
 *  upper to lower ( and viceversa) v2
 *
 *
 */

#include <unistd.h>
#include <st***.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <ctype.h>
#include <stdlib.h>



int main ( int nentry, char ** names ){

    int fd1,fd2,r_bytes,w_bytes,i;
    void * buffer;
    
    buffer = malloc(100);
    
    if (buffer == NULL){
        //impossibile allocare
        exit(-2);
    }
    
    fd1 = open (*(names +1 ),O_RDONLY);
    
    if (fd1 < 0){
        
        fprintf(stderr,"Sorgente non presente\n");
        exit (-3);
    }
    
    fd2 = open (*(names +2 ),O_WRONLY | O_TRUNC);
    
    if ( fd2<0){
        
        fprintf(stdout,"Creazione file destinazione in corso ..\n");
        fd2 = open (*(names +2 ),O_CREAT | O_WRONLY,00700);
        if (fd2<0){
            fprintf(stderr,"Impossibile creare file di destinazione\n");
            exit(-4);
        }
    }
    
    for (r_bytes= read( fd1, buffer, 100); r_bytes>0; r_bytes= read( fd1, buffer, 100)){
        
        for ( i=0;i<r_bytes;i++) {
            if ( islower(*((char *) buffer + i))){
                *((char *) buffer + i) = toupper(*((char *) buffer + i));
            }else{
                *((char *) buffer + i) = tolower(*((char *) buffer + i));
                
            }    
        }
        
        w_bytes = write (fd2,buffer,r_bytes);
        if ( w_bytes != r_bytes){
            
            fprintf(stderr,"Errore in scrittura sul file destinazione\n");
            exit(-5);
        }
        
    }
    
    if ( r_bytes < 0){
        
        fprintf(stderr, "Errore durante la lettura del file sorgente\n");
        exit(-6);
    }
    
   close(fd1);
   close(fd2);
  
   fprintf(stdout,"Operazione completata senza errori\n");
    
    return 0;
}