I'd like to use the time command in a bash script to calculate the elapsed time of the script and write that to a log file. I only need the real time, not the user and sys. Also need it in a decent format. e.g 00:00:00:00 (not like the standard output). I appreciate any advice.
The expected format supposed to be 00:00:00.0000
(milliseconds) [hours]:[minutes]:[seconds].[milliseconds]
I've already 3 scripts. I saw an example like this:
{ time { # section code goes here } } 2> timing.log
But I only need the real time, not the user and sys. Also need it in a decent format. e.g 00:00:00:00
(not like the standard output).
In other words, I'd like to know how to turn the time output into something easier to process.
You could use the date
command to get the current time before and after performing the work to be timed and calculate the difference like this:
#!/bin/bash
# Get time as a UNIX timestamp (seconds elapsed since Jan 1, 1970 0:00 UTC)
T="$(date +%s)"
# Do some work here
sleep 2
T="$(($(date +%s)-T))"
echo "Time in seconds: ${T}"
printf "Pretty format: %02d:%02d:%02d:%02d\n" "$((T/86400))" "$((T/3600%24))" "$((T/60%60))" "$((T%60))""
Notes: $((...)) can be used for basic arithmetic in bash – caution: do not put spaces before a minus - as this might be interpreted as a command-line option.
See also: http://tldp.org/LDP/abs/html/arithexp.html
EDIT:
Additionally, you may want to take a look at sed to search and extract substrings from the output generated by time.
EDIT:
Example for timing with milliseconds (actually nanoseconds but truncated to milliseconds here). Your version of date
has to support the %N
format and bash
should support large numbers.
# UNIX timestamp concatenated with nanoseconds
T="$(date +%s%N)"
# Do some work here
sleep 2
# Time interval in nanoseconds
T="$(($(date +%s%N)-T))"
# Seconds
S="$((T/1000000000))"
# Milliseconds
M="$((T/1000000))"
echo "Time in nanoseconds: ${T}"
printf "Pretty format: %02d:%02d:%02d:%02d.%03d\n" "$((S/86400))" "$((S/3600%24))" "$((S/60%60))" "$((S%60))" "${M}"
DISCLAIMER:
My original version said
M="$((T%1000000000/1000000))"
but this was edited out because it apparently did not work for some people whereas the new version reportedly did. I did not approve of this because I think that you have to use the remainder only but was outvoted.
Choose whatever fits you.