get help width from tty size

Author: NikolasK-source

src/main.cpp

@@ -43,9 +43,6 @@
 //! Maximum number of registers per type
 static constexpr size_t MODBUS_MAX_REGS = 0x10000;
 
-//! Help output line width
-static constexpr std::size_t HELP_WIDTH = 120;
-
 //! Default permissions for the created shared memory
 static constexpr mode_t DEFAULT_SHM_PERMISSIONS = 0660;
 
@@ -200,7 +197,15 @@ 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);
+        }
 #ifdef OS_LINUX
         if (isatty(STDIN_FILENO)) {
             struct winsize w {};