Programming

 
$ cat copy.c
#include <stdio.h>
#define PERMS 0644 /*  RW for owner, R for group, others */
#define BUFSIZE 1
char *progname;
int main(int argc,char * argv[])
{
        int f1, f2, n;
        char buf[BUFSIZE];
        progname = argv[0];
        if(argc != 3)
        printf("Usage %s from to\n", progname);
        f1 = open(argv[1], 0);
        if(f1 == -1)
        {
        printf("Can't open %s\n", argv[1]);
        }
        f2 = creat(argv[2], 777);
        if(f2 == -1)
        {
        printf("Can't create %s\n", argv[2]);
        }
        while((n = read(f1, buf, BUFSIZE)) > 0)
        {
                printf("%c\n", buf[0]);
                if(write(f2, buf, n) != n)
                {
                printf("Write error\n");
                }
        }
        exit(0);
}

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/stat.h>
#include <errno.h>

void  check_null( void *x ) 
{ 
	 if( x==NULL) 
	    { perror("Fatal error"); exit(1);}
}
ssize_t readall(int fd, char *buf, size_t bytes)
 {
     ssize_t bytes_read = 0;
     ssize_t n=0;

     do {
         if ((n = read(fd,
                       &buf[bytes_read],
                       bytes - bytes_read)) == -1)
         {
             if (errno == EINTR)  // resume on INTR
                 continue;
             else
                 return -1;
         }
         if (n == 0)
             return bytes_read;
         bytes_read += n;
     } while (bytes_read < bytes);
     return bytes_read;
 }

 // example use:

size_t filesize(const char *fname)
{
	  struct stat st;
	  if(stat(fname, &st) == -1)
	  {
	  	 fprintf(stderr, "cannot stat %s ", fname);
	  	 perror("");
	  	 exit(1);
	  }
	  return st.st_size;
}

int main(int argc, char **argv)
{
	  if(argc>1)
	  {
	  	 int i=1;
	  	 for( ;argv[i]!=NULL; i++)
	  	 {
	  	 	   size_t len=filesize(argv[i]);
	  	     char *buf=malloc(len);
	  	     FILE *in=fopen(argv[i], "r");	
	  	     check_null(buf);
	  	     check_null(in);
	  	     readall(fileno(in), buf, len);
	  	     printf("Read whole file %s: %u bytes\n", argv[i], len);
	  	     free(buf);	  
	  	     fclose(in);	     
	  	 }
	  	 return 0;
	  }
	  return 1;
}

> time readall bp.dat plpl 7084231.gpx.big before.txt after.txt
Read whole file bp.dat: 6962739 bytes
Read whole file plpl: 6800010 bytes
Read whole file 7084231.gpx.big: 1728412 bytes
Read whole file before.txt: 1584865 bytes
Read whole file after.txt: 1584892 bytes

real    0m0.362s
user    0m0.001s
sys     0m0.065s