bash time - ghdrako/doc_snipets GitHub Wiki
- https://www.cyberciti.biz/faq/unix-linux-time-command-examples-usage-syntax/
- https://github.com/ghdrako/doc_snipets/wiki/bash-date
- https://www.baeldung.com/linux/bash-calculate-time-elapsed
bash built-in variable SECONDS
Each time you reference the variable it will return the elapsed time since the script invocation.
echo "Start $SECONDS"
sleep 10
echo "Middle $SECONDS"
sleep 10
echo "End $SECONDS"
Output:
Start 0
Middle 10
End 20
time - build-in bash comand
TIMEFORMAT
| Value | Description |
|---|---|
| %% | A literal %. |
| %[p][l]R | The elapsed time in seconds. |
| %[p][l]U | The number of CPU seconds spent in user mode. |
| %[p][l]S | The number of CPU seconds spent in system mode. |
| %P | The CPU percentage, computed as (%U + %S) / %R. |
The optional p is a digit specifying the precision, the number of fractional digits after a decimal point. A value of 0 causes no decimal point or fraction to be output. At most three places after the decimal point may be specified; values of p greater than 3 are changed to 3. If p, is not specified, the value 3 is used. The optional l specifies a longer format, including minutes, of the form MMmSS.FFs. The value of p determines whether or not the fraction is included.
time command
$ cat elapsed_time.sh
TIMEFORMAT='It took %R seconds.'
time {
sleep 5
sleep 7
}
$./elapsed_time.sh
It took 12.008 seconds.
TIMEFORMAT='%3R' # The number specifies the precision and can range from 0 to 3 (the default). Format output 5.009 65.233
TIMEFORMAT='%3lR' # l gives long format Format output 3m10.022s
# Time format changes
TIMEFORMAT='%E elapsed'
# Function to be profiled
optimize_function() {
sleep 2
}
# Profile the function execution
time optimize_function
time external command
/usr/bin/time -f'%E' $CMD