Injecting Terminal Input.md

Injecting Terminal Input

Some examples demonstrating how to inject keystrokes into a terminal's input stream.

inject.bash

#!/bin/bash
bind '"\e[0n": "ls -l"'; printf '\e[5n'

inject.c

#include <stdlib.h>
#include <argp.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>

const char *argp_program_version ="inject - see http://unix.stackexchange.com/q/213799";
static char doc[] = "inject - write to terminal input stream";
static struct argp_option options[] = {
  { "tty",  't', "TTY", 0, "target tty (defaults to current)"},
  { "nonl", 'n', 0,     0, "do not output the trailing newline"},
  { 0 }
};

struct arguments
{
  int fd, nl, next;
};

static error_t parse_opt(int key, char *arg, struct argp_state *state) {
    struct arguments *arguments = state->input;
    switch (key)
      {
        case 't': arguments->fd = open(arg, O_WRONLY|O_NONBLOCK);
                  if (arguments->fd > 0)
                    break;
                  else
                    return EINVAL;
        case 'n': arguments->nl = 0; break;
        case ARGP_KEY_ARGS: arguments->next = state->next; return 0;
        default: return ARGP_ERR_UNKNOWN;
      }
    return 0;
}

static struct argp argp = { options, parse_opt, 0, doc };
static struct arguments arguments;

static void inject(char c)
{
  ioctl(arguments.fd, TIOCSTI, &c);
}

int main(int argc, char *argv[])
{
  arguments.fd=0;
  arguments.nl='\n';
  if (argp_parse (&argp, argc, argv, 0, 0, &arguments))
    {
      perror("Error");
      exit(errno);
    }


  int a,c;
  for (a=arguments.next, c=0; a< argc; c=0 )
    {
      while (argv[a][c])
        inject (argv[a][c++]);
      if (++a < argc) inject(' ');
    }
  if (arguments.nl) inject(arguments.nl);

  return 0;
}

inject.pl

#!/usr/bin/perl
require "sys/ioctl.ph";
ioctl(STDIN, &TIOCSTI, $_) for split "", join " ", @ARGV

inject.py

#!/usr/bin/python
import fcntl, sys, termios
del sys.argv[0]
for c in ' '.join(sys.argv):
  fcntl.ioctl(sys.stdin, termios.TIOCSTI, c)

inject.rb

#!/usr/bin/ruby
ARGV.join(' ').split('').each { |c| $stdin.ioctl(0x5412,c) }

typeahead

#!/bin/bash
# Example wrapper around injected terminal input to
# prevent premature echo in front of the prompt.

# A more basic solution is to have the prompt pre-clear its line
# which can be done by prefixing it with "\r\e[M"

inject() {
  if [[ $0 == "$BASH_SOURCE" ]] # executed or sourced ?
  then
    # ioctl TIOCSTI method works best (it works if sourced or executed)
    echo using ioctl method
    perl -e 'ioctl(STDIN, 0x5412, $_) for split "", join " ", @ARGV' "$@" ""
  else
    # escape method only works if script is sourced
    echo using bind method
    bind "\"\e[0n\": '$*'"; printf '\e[5n'
  fi
}

saved_settings=$(stty -g)
stty -echo -icanon min 1 time 0
inject echo $*
until read -t0; do
  sleep 0.02
done
stty "$saved_settings"