Obsoleted by xdotool at the time of its creation without me knowing for a couple of years.

send.c

// gcc -Wall -Wextra -ggdb -o send send.c

#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/keysym.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <X11/keysymdef.h>

#define XK_leftarrow                     0x08fb  /* U+2190 LEFTWARDS ARROW */
#define XK_uparrow                       0x08fc  /* U+2191 UPWARDS ARROW */
#define XK_rightarrow                    0x08fd  /* U+2192 RIGHTWARDS ARROW */
#define XK_downarrow                     0x08fe  /* U+2193 DOWNWARDS ARROW */

Display* dply;
Window w;

void die(char* cause)
{
    printf("%s\n", cause);
    exit(1);
}

void XGetFocusedWindow(Display* dpy, Window* w)
{
    int iret;
    XGetInputFocus(dpy, w, &iret);

    if (*w == None)
        die("nofocus");
}

void gen_event(XKeyEvent *e)
{
    memset(e, 0, sizeof(*e));
    e->type          = KeyPress;
    e->time          = CurrentTime;
    e->display       = dply;
    e->window        = w;
    e->subwindow     = None;
    e->root          = DefaultRootWindow(dply);
    e->x             = 1;
    e->y             = 1;
    e->x_root        = 1;
    e->y_root        = 1;
    e->same_screen   = 1;
}

void set_btn(XKeyEvent *e, KeySym sym)
{
    e->keycode       = XKeysymToKeycode(dply, sym);
}

int main(int argc, char** argv)
{
    int i, len;
    KeySym key;
    XKeyEvent e;

    if (argc != 2 || (dply = XOpenDisplay(NULL)) == NULL)
        die("argc / display");

    XGetFocusedWindow(dply, &w);

    gen_event(&e);

    len = strlen(argv[1]);
    for (i = 0; i < len; i++) {
        key = argv[1][i];
        switch (key) {
            case '\n':
                key = XK_Return;
                break;
            case '\t':
                key = XK_Return;
                break;
            case '<':
                key = XK_leftarrow;
                break;
            case '>':
                key = XK_rightarrow;
                break;
            case 'A':
                key = XK_Page_Up;
                break;
            case 'V':
                key = XK_Page_Down;
                break;
            case '+':
                key = XK_F11;
                break;
        }
        set_btn(&e, key);

        e.type          = KeyPress;
        XSendEvent(dply, w, 1, KeyPressMask,    (XEvent*) &e);
        XFlush(dply);
        e.type          = KeyRelease;
        XSendEvent(dply, w, 1, KeyReleaseMask,  (XEvent*) &e);
        XFlush(dply);

        usleep(250);
    }

    XCloseDisplay(dply);

    return 0;
}