Create random password keys of argument length

keygen.cpp

#include <stdlib.h>
#include <chrono>
#include <iostream>
#include <random>
#include <string>
#include <sstream>

#define NUMKEYS 71

static char keys[] = {'a', 'b', 'c' ,'d' ,'e' ,'f' ,'g' ,'h' ,'i' ,'j' ,'k' ,'l' ,'m' ,'n' ,'o' ,'p' ,'q' ,'r' ,'s' ,'t' ,'u' ,'v' ,'w' ,'x' ,'y' ,'z' ,'A' ,'B' ,'C' ,'D' ,'E' ,'F' ,'G' ,'H' ,'I' ,'J' ,'K' ,'L' ,'M' ,'N' ,'O' ,'P' ,'Q' ,'R' ,'S' ,'T' ,'U' ,'V' ,'W' ,'X' ,'Y' ,'Z' ,'0' ,'1' ,'2' ,'3' ,'4' ,'5' ,'6' ,'7' ,'8' ,'9' ,'!' ,'@' ,'#' ,'$' ,'%', '^', '&', '-', '_'};


void generate(int keyLen)
{
	unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
	std::mt19937 eng(seed);
	//std::default_random_engine eng;
	std::uniform_int_distribution<int> dist(0,NUMKEYS-1);


	std::stringstream buffer;
	for (int bufpos = 0; bufpos < keyLen; ++bufpos) {
		buffer << keys[dist(eng)];
	}
	std::cout << buffer.str() << std::endl;
}

inline void usage()
{
	std::cerr << "Usage: keygen <key length>" << std::endl;
}

int main(int argc, char **argv)
{
	if (argc == 2) {
		int keyLen = strtol(argv[1], NULL, 10);
		if (keyLen > 0)
			generate(keyLen);
		else
			usage();
	} else if (argc == 1)
		generate(15);
	else {
		usage();
		return 1;
	}
	return 0;
}

Makefile

CFLAGS=-W -Wall -g -std=c++11 -Wextra -pedantic

keygen: keygen.o
	g++ $(CFLAGS) -o keygen keygen.o

keygen.o: keygen.cpp
	g++ $(CFLAGS) -c keygen.cpp

.PHONY: clean
clean:
	rm -f keygen keygen.o