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Eval not showing correct date format in bash script

This is my script

#!/bin/bash
EXPIRYTIME=30
dateformat=(date -d \"+ $EXPIRYTIME minutes\" +"%Y-%m-%dT%H-%M-%S+00:00")
#dateformat=(date + "%Y-%m-%dT%H-%M-%S+00:00")
expiry=$(eval $dateformat)

And it is showing wrong results, that is Fri Aug 14 14:36:17 IST 2020\

But when I run in my cli it is showing right format that is: 2020-08-14T15-03-52+00:00

Can anyone help me in this?

Solution

  • The main problem is with this line:

    dateformat=(date -d \"+ $EXPIRYTIME minutes\" +"%Y-%m-%dT%H-%M-%S+00:00")

    where the =(...) says to assign an array of values to the dateformat variable.

    Then eval $dateformat fails to provide an array subscript so bash will use whatever value is assigned to index=0 which in this case is date; net result is that you end up running date (with no args) and you get the current date/time.

    You have a couple options:

    1 - continue to use the array but make sure you reference the entire set of array indices:

    $ dateformat=(date -d \"+ $EXPIRYTIME minutes\" +"%Y-%m-%dT%H-%M-%S+00:00")
$ eval "${dateformat[@]}"
2020-08-14T04-53-55+00:00

    2 - define the variable as a single string:

    $ dateformat='date -d "+ '"${EXPIRYTIME}"' minutes" +"%Y-%m-%dT%H-%M-%S+00:00"'
$ eval "${dateformat}"
2020-08-14T04-53-57+00:00

    Keep in mind for this particular case there's no need for the eval as ${EXPIRYTIME} can be fed directly to the date command:

    $ date -d "+ ${EXPIRYTIME} minutes" +"%Y-%m-%dT%H-%M-%S+00:00"
2020-08-14T04-53-58+00:00

    NOTE: The above examples were run when local system time was Fri Aug 14 04:23:55 CDT 2020