typer

#!/usr/bin/env bash
# typer - pipe in, type out
# typer © Mike Lalumiere 2019
typer() {
    # usage
    read -r -d '' use <<EOF
USAGE: typer [OPTIONS] < TEXT
Write text input delayed to simulate typing.

OPTIONS:
 -h      : Print some help text
 -c RATE : Print rate in characters per second (0-999)
 -r      : Randomized delay between characters (default)
 -s      : Smooth output, no randomization

EXAMPLES:
 $> typer -c 5 <<< "Hello, \$USER..."
 $> typer -r -c 50 < <(fortune)
 $> nethack | typer -c 600
 $> ttyrec /dev/null | typer -s -c 900

(c) Mike Lalumiere 2019
EOF
    # return nicely on interrupt
    trap 'printf "\n"; return 2' SIGINT
    # get options
    local rate=30 mode="random"
    local opt OPTIND OPTARG
    while getopts ":hc:qrs" opt; do
        case "$opt" in
            c) # rate in characters per second 0-999
                rate="$OPTARG"
                if [[ "$rate" -ge 1000 ]] || [[ "$rate" -le 0 ]]; then
                    printf "Rate must be between 1 and 999.\\n" >&2
                    return 2
                fi
                ;;
            r) # random mode
                mode="random"
                ;;
            s) # smooth mode
                mode="smooth"
                ;;
            q) # quick mode
                mode="quick"
                ;;
            h) # help?
                printf "%s\\n" "$use"
                return 1
                ;;
            \?) # invalid
                printf  "Invalid option: -%s\\n\\n%s\\n" "$OPTARG" "$use" >&2
                return 1
                ;;
        esac
    done
    # speed things up
    if (( rate < 5 )); then
        rate=0
    fi

    # read one character at a time from standard input
    local delay=0
    while IFS= read -r -N 1 c; do
        # calculate delay in thousanths of a second
        case "$mode" in
            smooth)
                delay=$(printf "0.%03d" $(( 1000 / rate )) )
                ;;
            random)
                delay=$(printf "0.%03d" $(( RANDOM % ( 2000 / rate ) )) )
                ;;
            quick)
                delay=0
                ;;
        esac
        # delay that long
        if [ "$delay" != "0.000" ]; then
            sleep "$delay"
        fi
        # write the character
        printf "%s" "$c"
    done
}
# run it unless sourced
if [[ "${BASH_SOURCE[0]}" == "$0" ]]; then typer "$@"; fi