get help width from tty size

Author: NikolasK-source

src/main.cpp

@@ -12,11 +12,9 @@
 #include <filesystem>
 #include <iostream>
 #include <memory>
+#include <sys/ioctl.h>
 #include <sysexits.h>
 
-//! Help output line width
-static constexpr std::size_t HELP_WIDTH = 120;
-
 int main(int argc, char **argv) {
     const std::string exe_name = std::filesystem::path(*argv).filename().string();
     cxxopts::Options  options(exe_name, "Writes the content of stdin to a named shared memory.");
@@ -61,7 +59,15 @@ int main(int argc, char **argv) {
 
     // print usage
     if (args.count("help")) {
-        options.set_width(HELP_WIDTH);
+        static constexpr std::size_t MIN_HELP_SIZE = 80;
+        if (isatty(STDIN_FILENO)) {
+            struct winsize w {};
+            if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &w) != -1) {  // NOLINT
+                options.set_width(std::max(static_cast<decltype(w.ws_col)>(MIN_HELP_SIZE), w.ws_col));
+            }
+        } else {
+            options.set_width(MIN_HELP_SIZE);
+        }
         std::cout << options.help() << '\n';
         std::cout << "This application uses the following libraries:" << '\n';
         std::cout << "  - cxxopts by jarro2783 (https://github.com/jarro2783/cxxopts)" << '\n';