watch like script

rep.sh

#!/bin/bash
#
# st_repeat HELP:
# st_repeat [-d <delay>] [-i] [-c <count>] [-k] <command>
# Repeat the given command.
#
# By default, this command will exit upon success, unless -i or -c are given.
#
# -d (default 2) specifies how long to wait between iterations
# -i will repeat the command indefinitely
# -c will repeat the command the specified number of times
# -k will clear the screen before each iteration
# ENDHELP

tt=/tmp/rep.$$

trap 'rm -f $tt;exit' 0

unset OPTIND;

delay=2;
on_success=1;
infinite=1;
count=-1;
clear=1;

while getopts ":d:sikc:" options; do
    case $options in
        d ) delay=${OPTARG};
            ;;
        i ) infinite=1;
            ;;
        c ) count=${OPTARG};
            ;;
        k ) clear=0;
            ;;
        * ) st_help st_repeat;
            return 1;
            ;;
    esac;
done;

[ ${infinite} -eq 1 ] && [ ${count} -gt -1 ] && \
    echo "You can only give a count or specify infinity" && return 1

shift $((${OPTIND} - 1))

i=1;
while [ 1 ]; do
    [ ${clear} -eq 1 ] && clear > $tt;

    date +%T >> $tt
    echo "" >> $tt
    "$@" >> $tt
    status=$?
    cat $tt

    # if on_success was specified and exit status was 0, break
    [ ${infinite} -ne 1 ] && \
        [ ${count} -lt 0 ] && \
        [ ${on_success} -eq 1 ] && \
        [ ${status} -eq 0 ] && break;

    let i="${i} + 1";
    
    # if a count was specified, break
    [ ${infinite} -ne 1 ] && \
        [ ${count} -gt -1 ] && \
        [ ${i} -gt ${count} ] &&  break;

    # sleep
    sleep ${delay}
done;