bash shell scripting: create an endtime from a starttime - bash

Question

I am mediating some data from one file-format to another and am using bash to perform the mediation steps. Part of the process involves taking a timestamp from the filename to create a starttime and then adding 5 minutes to that to create the endtime. The filename gives me a date in this format YYYYmmddHHMMSS. I can easily add 500 to each starttime to get an endtime that works for all starttimes except 55 mins past the hour but this obviously not correct so I have tried to use the date --date= code to add the 5minutes like this:
date --date='$starttime +5 minutes' '+%Y%m%d%H%M%S'
for example:
date --date='20140220125500 +5 minutes' '+%Y%m%d%H%M%S'
However I get an error like this every time:
date: invalid date `20140220125500 +5 minutes'
Can anyone suggest what I need to change in my date statement or if there is a similar alternative syntax available?

Answer 1

This worked to me:
$ date --date='20140220 12:55:00 CET +5 minutes' '+%Y%m%d%H%M%S'
20140220130000
That is, the problem is that YYYYYMMDDHHMMSS alone is not understandable for date. Instead, give it on the YYYYYMMDD HH:MM:SS format.
As you are receiving the data on that YYYYYMMDDHHMMSS format, you can parse it with sed as follows:
$ file="YYYYmmddHHMMSS"
$ new_name=$(sed -e 's/^\(.\{8\}\)\(.\{2\}\)\(.\{2\}\)\(.\{2\}\)/\1 \2:\3:\4/' <<< "$file")
$ echo "$new_name"
YYYYmmdd HH:MM:SS
So in your case:
$ file="20140220125500"
$ new_name=$(sed -e 's/^\(.\{8\}\)\(.\{2\}\)\(.\{2\}\)\(.\{2\}\)/\1 \2:\3:\4/' <<< "$file")
$ echo "$new_name"
20140220 12:55:00
$ date --date="$new_name CET + 5 minutes"
Thu Feb 20 13:00:00 CET 2014
Note I used
$ date --date="$new_name CET +5 minutes" '+%Y%m%d%H%M%S'
^ ^
note the double quotes to have the var expanded