Summary - Terminal I/O

Combine termios and ANSI to write a terminal app.

Terminal I/O summary

You learned the terminal I/O toolkit: termios for reading settings, raw mode for instant keys, non-blocking for non-waiting reads, ANSI for color and cursor, ioctl for size. These are the foundation of interactive apps.

In this summary we will combine termios, fcntl and ioctl into a terminal preparation app. Using them together shows how real CLI tools are built. The output is deterministic: we print a fixed ready message.

Exercise Prepare the terminal

Read settings with struct termios t; tcgetattr(STDIN_FILENO, &t);. Switch to non-blocking mode with fcntl(STDIN_FILENO, F_SETFL, O_NONBLOCK);. Declare struct winsize ws; ws.ws_row = 24; ws.ws_col = 80; and call (void)ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws);. Print with printf("terminal ready\n");.

Show example solution

#include <stdio.h>
#include <termios.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>

int main(void) {
    struct termios t;
    tcgetattr(STDIN_FILENO, &t);
    fcntl(STDIN_FILENO, F_SETFL, O_NONBLOCK);
    struct winsize ws;
    ws.ws_row = 24;
    ws.ws_col = 80;
    (void)ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws);
    printf("terminal ready\n");
    return 0;
}

Next steps

You completed terminal I/O. These foundations are the core of text editors, shells and TUI apps. With termios and raw mode you get key-by-key input, with ANSI colors, with ioctl the size.

Next topics: dynamic loading for plugin systems and cryptography for security. Combined with terminal apps, they form powerful CLI tools.

Test yourself

Which tool is used for colored output?
- flock
- fcntl
- shmget
- ANSI escape
Show answer

ANSI escape — ANSI escape sequences are used for color and formatting.
Match terminal tools

termios

Read settings
cfmakeraw

Raw mode
O_NONBLOCK

Non-blocking
ioctl

Size

Next lesson: dlopen

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