I have two text files. One file has startdatetime and second file have enddatetime.
file 1 data(startdate-time):
2019-01-08 04:14:59
2019-01-08 04:16:57
file 2 data(enddate-time):
2019-01-08 04:15:50
2019-01-08 04:17:02
I need Unix script which will perform operation on endtime - starttime (only on time). Example for first entry it should perform:
04:15:50 - 04:14:59
and give result in seconds (for this example, it should print total difference seconds)
There is a cross-platform set of command line utilities called Dateutils which includes a datediff command. If you are on Linux, there is a good chance you can install dateutils using your package manager.
You haven't stated whether you want this for Linux, Mac, a BSD or some other Unix, so the following might need tweaking for your needs, but it works for me on Arch Linux:
$ paste start.txt end.txt | sed 's/ /T/g' | while read dates; do datediff $dates; done
51s
5s
You can think of the pipeline as consisting of two parts: the while read dates; do datediff $dates; done which feeds any input to datediff for calculating the difference; and the paste start.txt end.txt | sed 's/ /T/g' part which preprocesses the raw data into a form suitable for consumption by datediff.
In particular, given the example inputs you've provided, you need to worry about escaping spaces; if the data were left in its raw form, datediff would think each space in the file indicates a separate argument. For example, this would not be suitable input:
$ paste start.txt end.txt
2019-01-08 04:14:59 2019-01-08 04:15:50
2019-01-08 04:16:57 2019-01-08 04:17:02
Therefore I use sed to replace the spaces (not tabs) with T, to match some examples from the datediff manual (man datediff):
$ paste start.txt end.txt | sed 's/ /T/g'
2019-01-08T04:14:59 2019-01-08T04:15:50
2019-01-08T04:16:57 2019-01-08T04:17:02
This data now only has spaces in between the intended arguments, and each argument is in a form that matches examples provided in the manual.
datediff in /bin, /usr/bin or /usr/local/bin, but you will be able to install it in $HOME/bin/
A solution that uses bash and GNU date:
#!/bin/bash
while IFS= read -r -u3 line1; do
IFS= read -r -u4 line2
start_date="$line1"
end_date="$line2"
difference=$(( $(date -d "$end_date" "+%s") - $(date -d "$start_date" "+%s") ))
echo "Start Date: $start_date; End Date: $end_date; Difference in seconds = $difference"
done 3<start-times.txt 4<end-times.txt
The file descriptors 3 & 4 are used to read from both files, one line at a time. From there, the GNU date command is used to convert them to epoch time. Bash's arithmetic expansion is used to calculate the difference.
Sample output:
Start Date: 2019-01-08 04:14:59; End Date: 2019-01-08 04:15:50; Difference in seconds = 51
Start Date: 2019-01-08 04:16:57; End Date: 2019-01-08 04:17:02; Difference in seconds = 5
