unite.c

// unite files to one
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

#define MAXNAME 100

// routines
void showusage();
void diskwritefailure();

// constants & variables
char *myname;

int main(int argc, char *argv[])
{
  int i, c, infile, outfile;
  char buf[BUFSIZ], destinationfilename[MAXNAME];
  size_t nread, nwrite;
  strcpy((myname=malloc(sizeof(argv[0]))), argv[0]);

    // parse command line options
    while ((c=getopt(argc, argv, ":o:")) != -1)
     switch (c) {
      case 'o':
       strcpy(destinationfilename, optarg);
      break;
      case '?':
       showusage();
      break;
      default:
       abort();
    break; }
    if (argc<3)
     showusage();
    if ((outfile=open(destinationfilename, O_WRONLY| O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR))==-1)
     diskwritefailure();

   // unite files
   for (i=optind;i<argc;i++) {
    if ((infile=open(argv[i], O_RDONLY))==-1)
     break;
    while ((nread=read(infile, buf, sizeof(buf))))
     if ((nwrite=write(outfile, buf, nread)==-1))
    diskwritefailure();
   close(infile); }
   close(outfile);

 return 0;
}

// show usage
void showusage()
{
  printf("%s [-o output file] [files ...]\n", myname);

 exit(EXIT_FAILURE);
}

// error writing to disk
void diskwritefailure()
{
  printf("error writing to disk!\n");

 exit(EXIT_FAILURE);
}