Date format in bash

Question

Simple bash question... I suppose, I'm new.

I have substract date from system time

date_from=`date -d "30 minutes ago"`

after, I want format the result in $date_from in 'yyyy-mm-dd'

how can I do that?

Answer 1

date -d "30 minutes ago" +%Y-%m-%d

不过，很可能在30分钟前的同一天:)

Answer 2

您可以附加格式字符串：

date -d "30 minutes ago" +"%Y-%m-%d"

Answer 3

As you can't guarantee that 30 minutes ago would be the same day, your best solution would be convert the current date/time into seconds from 1970, subtract 30*60 seconds, and then convert this back into a date.

I could do this in a script, not sure how to do it in one line.

Something like:

CURRENT=date +%S
CURRENTMINUS30=expr $CURRENT - (30*60)
OLD = date -d@`CURRENTMINUS30`

That's untested though. I'll have a go at getting the script to work and post it's contents, and perhaps someone else can do it in one line.