i need to get the running time of a program as soon as it is closed and i came up with this
start=`date +"%M"`
while [ `pgrep vlc` ];do
echo vlcopen > /dev/null
done
stop=`date +"%M"`
[ $stop -lt $start ]&&time=$[ 60-$start+$stop ]||time=$[ $stop-$start ]
echo $time > time.txt
and it does the job but this is highly inefficient and takes a lot of cup usage how do i do this more efficiently
One option is to use time
Note: Bash has a keyword time so if you do:
time some command
that one is used , SHELL_GRAMMAR: bash
The time you find in man time is usually something like /usr/bin/time
$ type -t time
keyword
Main point in using the non bash time is features like -v (GNU time).
Also see: What do 'real', 'user' and 'sys' mean in the output of time(1)?
time with the TIMEFORMAT variable. e.g. TIMEFORMAT=$'\nreal %3lR\tuser %3lU\tsys %3lS' is, IMO, a nice simple one-line format (I set this in my ~/.bashrc). The GNU version of /usr/bin/time (i.e. not the bash built-in) uses the TIME variable instead.
Use the bash SECONDS variable:
SECONDS=0
# do stuff here, such as
sleep 5
duration=$SECONDS
echo "The stuff took $duration seconds to complete"
Efficiency is gained by removing the need to spawn external processes.
man time. We have a tool for that.