Stop Watch script added

Shell/stop_watch.sh

@@ -0,0 +1,107 @@
+#!/bin/sh
+
+# Notes:
+#    This script starts a few processes per lap, in addition to
+#    the shell loop processing, so the assumption is made that
+#    this takes an insignificant amount of time compared to
+#    the response time of humans (~.1s) (or the keyboard
+#    interrupt rate (~.05s)).
+#    '?' for splits must be entered twice if characters
+#    (erroneously) entered before it (on the same line).
+#    '?' since not generating a signal may be slightly delayed
+#    on heavily loaded systems.
+
+
+export LANG=C
+
+ulimit -c 0   # No coredumps from SIGQUIT.
+trap '' TSTP  # Ignore Ctrl-Z just in case.
+save_tty=`stty -g` && trap "stty $save_tty" EXIT  # Restore tty on exit.
+stty quit ' ' # Space for laps rather than Ctrl-\.
+stty eof  '?' # ? for splits rather than Ctrl-D.
+stty -echo    # Don't echo input.
+
+cache_progs() {
+    stty > /dev/null
+    date > /dev/null
+    grep . < /dev/null
+    (echo "import time" | python) 2> /dev/null
+    bc < /dev/null
+    sed '' < /dev/null
+    printf '1' > /dev/null
+    /usr/bin/time false 2> /dev/null
+    cat < /dev/null
+}
+cache_progs   # To minimise startup delay.
+
+date +%s.%N | grep -qF 'N' && use_python=1 # If `date` lacks nanoseconds.
+now() {
+    if [ "$use_python" ]; then
+        echo "import time; print time.time()" 2>/dev/null | python
+    else
+        printf "%.2f" `date +%s.%N`
+    fi
+}
+
+fmt_seconds() {
+    seconds=$1
+    mins=`echo $seconds/60 | bc`
+    if [ "$mins" != "0" ]; then
+        seconds=`echo "$seconds - ($mins*60)" | bc`
+        echo "$mins:$seconds"
+    else
+        echo "$seconds"
+    fi
+}
+
+total() {
+    end=`now`
+    total=`echo "$end - $start" | bc`
+    fmt_seconds $total
+}
+
+stop() {
+    [ "$lapped" ] && lap "$laptime" "display"
+    total
+    exit
+}
+
+lap() {
+    laptime=`echo "$1" | sed -n 's/.*real[^0-9.]*\(.*\)/\1/p'`
+    [ ! "$laptime" -o "$laptime" = "0.00" ] && return
+    # Signals too frequent.
+    laptotal=`echo $laptime+0$laptotal | bc`
+    if [ "$2" = "display" ]; then
+        lapcount=`echo 0$lapcount+1 | bc`
+        laptime=`fmt_seconds $laptotal`
+        echo $laptime "($lapcount)"
+        lapped="true"
+        laptotal="0"
+    fi
+}
+
+echo -n "Space for lap | ? for split | Ctrl-C to stop | Space to start...">&2
+
+while true; do
+    trap true INT QUIT  # Set signal handlers.
+    laptime=`/usr/bin/time -p 2>&1 cat >/dev/null`
+    ret=$?
+    trap '' INT QUIT    # Ignore signals within this script.
+    if [ $ret -eq 1 -o $ret -eq 2 -o $ret -eq 130 ]; then # SIGINT = stop
+        [ ! "$start" ] && { echo >&2; exit; }
+        stop
+    elif [ $ret -eq 3 -o $ret -eq 131 ]; then             # SIGQUIT = lap
+        if [ ! "$start" ]; then
+            start=`now` || exit 1
+            echo >&2
+            continue
+        fi
+        lap "$laptime" "display"
+    else                # eof = split
+        [ ! "$start" ] && continue
+        total
+        lap "$laptime"  # Update laptotal.
+    fi
+done
+
+exit $?