CODEWITHSUNDEEP
bashdatevariables
Mr.Mongo
Mr.Mongo

Reputation: 7

Bash date subtraction +%H:%M:%S

I looked all over online and can't seem to find anything that addresses what I am trying to do. I am using Bash on an Unbuntu VM. I created the following script

start_code=$(date +%H:%M:%S)
end_code=$(date +%H:%M:%S)
echo $start_code
for i in {1..1000};
 do echo $RANDOM >> filename.txt;
done
echo $end_code

The code works fine, but is there any way that I can subtract the variables start_code from end_code??

I have tried this many different ways one being total_code=$(($start_code - $end_code)) but I get errors or nothing returned with everything that I have tried. As I'm brand new to Bash and I'm not even sure if I can do this. Any help would be greatly appreciated.

Upvotes: 0

Views: 285

Answers (1)

William Pursell
William Pursell

Reputation: 212198

There are better ways to compute time lapsed. You can do the subtraction with something like:

$ cat a.sh
#!/bin/sh

foo() {
        # This function does stuff
        sleep ${1-2}
}
start=$(date +%s)
foo 3
end=$(date +%s)

echo "time lapsed: $((end - start))"

time foo 4
$ ./a.sh
time lapsed: 3

real    0m4.006s
user    0m0.001s
sys     0m0.001s

In the above, we first store a time stamp before calling the function foo that just sleeps for 3 seconds. Then we compute a new time stamp and subtract. Then we do the same using the time builtin and let the function sleep for 4 seconds.

Upvotes: 1

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