password.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#define MAXSIZE 65536

char pw[MAXSIZE];
void print_usage();
int randomizebuff(char *buff, int start, int end, int buffsize);
int number(char *st);

int main(int argc, char *argv[])
{
  srand(time(NULL)); 
  // have to do `srand` in main, 
  // else it will seed the same value each time through `randomize` 
  //and repeat the same random sequences 
  
  int thisnum=0;
  int pwindex=0;

  if (argc < 2) {
    pwindex = 12;
    randomizebuff(pw, 0, pwindex, MAXSIZE);
  }
  
  else if ((strcmp(argv[1], "-h") == 0) || (strcmp(argv[1], "--help") == 0)) {
    print_usage(argv[0]);
    return 1;
  }


  
  else {

    for (int i=1; i<argc; i++) {
      if((thisnum=number(argv[i]))) {
        if (!randomizebuff(pw, pwindex, pwindex+thisnum, MAXSIZE)) {
          printf("oops\n"); 
          return 1;
        }
        pwindex+=thisnum;
      }
      else {
        for(int j=0; j<strlen(argv[i]); j++)
          pw[pwindex++] = argv[i][j];
      }
    }
  }

  pw[pwindex]='\0';
  printf("%s\n", pw);
  return 0;
}

int number(char *buff) {
  char c;
  int i=0;
  int val=0;
  while((c = buff[i++]) != '\0') {
    if (c >= '0' && c <= '9') {
      val = val*10 + atoi(&c);
    }
    else {
      return 0;
    }
  }
  return val;
}


  
int randomizebuff(char *buff, int start, int end, int buffsize)
{
  char vals[64] = "023456789abcdefghikmnopqrstuvwxyzABCDEFGHKLMNPQRSTUVWXYZ!@#$%^&*";
  if (end >= buffsize || start < 0) {
    return 0; // not enough space
  }
  for (int i=start; i<end; i++)
  {
    buff[i] = vals[rand()%64];
  }
  return 1;
}

void print_usage(char *st) 
{
  printf("%s\n\t%s%s\n\t%s %s\n\t%s", "usage:", st, " num str num str ...", st, 
	 "creates a random password by appending num random chars to str", 
	 "For example, with inputs of 'asdf', '5', and 'zwr'\n\tit would output something like 'asdfc4q80zwr'");
}