29: cat

Implement the first command line tool, cat.

View Source file cat.cpp Only

// https://www.gnu.org/software/coreutils/manual/html_node/cat-invocation.html

#include <iostream>
#include <fstream>
#include <string>
#include <fmt/core.h>
#include <unistd.h>

void dump_file(std::istream& in, bool number, bool squeeze) {
  std::string line;
  int line_count = 0;

  while(in) {
    getline(in, line);
    line_count++;

    if(line == "" && squeeze) continue;

    if(number) {
      fmt::println("{}: {}", line_count, line);
    } else {
      fmt::println("{}", line);
    }
  }
}

int main(int argc, char* argv[]) {
  int opt = 0;
  bool number = false;
  bool squeeze = false;

  while((opt = getopt(argc, argv, "ns")) != -1) {
    switch(opt) {
      case 'n':
        number = true;
        break;
      case 's':
        squeeze = true;
        break;
      default:
        fmt::print("USAGE: cat -ns [file]");
        return 1;
    }
  }

  if(optind < argc) {
    // there's files to process
    for(int i = optind; i < argc; i++) {
      std::ifstream in_file{argv[i]};
      dump_file(in_file, number, squeeze);
    }
  } else {
    dump_file(std::cin, number, squeeze);
  }
}