Differences

This shows you the differences between two versions of the page.

--- lecture_materials:week_00 [2025-08-18 22:07] – Jeffrey Bergamini
+++ lecture_materials:week_00 [2025-08-19 14:31] (current) – Jeffrey Bergamini
@@ Line 119: / Line 119: @@
 === raii.cpp (illustrating the concept of RAII) ===
-<file cpp scopes_annotated.cpp [enable_line_numbers=true]>
+<file cpp raii.cpp [enable_line_numbers=true]>
 /**
  * @file raii.cpp
@@ Line 163: / Line 163: @@
   std::ifstream othello{"/srv/datasets/shakespeare-othello.txt"};
   std::cout << "Othello: " << count_vowels(othello) << '\n';
-  // std::cout is just a plain input stream:
+  // std::cin is just a plain input stream:
   std::cout << "std::cin: " << count_vowels(std::cin) << '\n';
   // Lifetimes of `hamlet` and `othello` end here.
@@ Line 186: / Line 186: @@
  */
-#include <cctype>    // `std::isprint()`
+#include <cctype>    // for `std::isprint()`
-#include <fstream>   // `std::ifstream`
+#include <fstream>   // for `std::ifstream`
-#include <iostream>  // `std::cout`
+#include <iostream>  // for `std::cout`
+/**
+ * `main()` can have parameters to access *command-line arguments* and *environment variables*.
+ *
+ * @param argc argument count: the number of command-line arguments (including the executable name)
+ * @param argv argument values: an array of C strings containing the command-line arguments
+ */
 int main(int argc, char **argv) {
+  // Exit with an error message if command-line arguments weren't provided:
+  if (argc < 3) {
+    std::cerr << "Usage: " << argv[0] << " FILE1 FILE2\n";
+    return 1;  // nonzero exit status reports unsuccessful termination to the shell
+  }
+  // Attempt to open the two files specified as command-line arguments:
   std::ifstream f1(argv[1]);
   std::ifstream f2(argv[2]);
-  // TODO: Find all the printable characters unique present in one file and not the other.
+  if (!f1 || !f2) {
-  // Print each unique character and its ASCII number, one character per line, in ascending order.
+    std::cerr << "Cannot read from input file(s)\n";
+    return 2;
+  }
+  // TODO: Find all the unique printable characters present in one file and not the other.
+  // Print each unique character and its ASCII encoding, one character per line, in ascending order.
 }
 </file>