safe_sleep.sh

#!/bin/bash

# try to use sleep if available
if [ -x "$(command -v sleep)" ]; then
    sleep "$1"
    exit 0
fi

# assert integer
if ! builtin printf %d "$1" &>/dev/null; then
    echo "safe_sleep: invalid time interval ‘$1’"
    exit 1
fi

# try to use ping if available
if [ -x "$(command -v ping)" ]; then
    ping -c $(( $1 + 1 )) 127.0.0.1 > /dev/null
    exit 0
fi

# try to use read -t from stdin/stdout/stderr if we are in bash
if [ -n "$BASH_VERSION" ]; then
    if command -v read >/dev/null 2>&1; then
        if [ -t 0 ]; then
            read -t "$1" -u 0 || :;
            exit 0
        fi
        if [ -t 1 ]; then
            read -t "$1" -u 1 || :;
            exit 0
        fi
        if [ -t 2 ]; then
            read -t "$1" -u 2 || :;
            exit 0
        fi
    fi
fi

# fallback to a busy wait
SECONDS=0
while [[ $SECONDS -lt $1 ]]; do
    :
done