I am trying to calculate the current date MMYY - 15 months ago.
I get current date in the format I want with shell command: date +"%m%y"
I am trying to use this current date and calculate what the MMYY is 15 months ago, what command would show me this?
Not sure why you want to get the current MMYY and calculate "15 months ago" afterwards. You could just do it in one command:
date --date='15 months ago' +"%m%y"
man date and info date are your friend.
Related
This question already has answers here:
Bash script compare two date variables [duplicate]
(5 answers)
Closed 1 year ago.
I have to read a epoch timestamp (in seconds) from a directory /usr/local/healthcheck.txt on my Red Hate Enterprise Linux machine every ~10 minutes (polling). I need perform a comparison on the time to check if the timestamp in the healthcheck.txt file is OLDER than 50 minutes from the current time/timestamp OR if the healthcheck.txt is non-existent, to throw an error. The timestamp in the healthcheck.txt file generally looks like this (its in seconds, as stated above) :
1591783065
I was using date -d #1591783065 to convert the timestamp to Human Readable and get something like this:
Tue Jun 9 16:22:57 UTC 2020
What would be the best approach to compare the current timestamp to this timestamp in the file and check if its older than 50 minutes?
In Java , we have a Date package , and can just use compareTo to compare the times/dates, is there a simple way to do this with shell/bash scripts?
Why don't you stick with epoch-time? You can get the current time as seconds since epoch by
date +%s, so you just have to compare
if (( (healthcheck_time + 50*60) < $(date +%s) ))
then
# .... healthcheck older than 50 minutes
fi
I'm trying to calculate the seconds between a date from now, however, I always get extra one day when adding the seconds from now.
echo $(($(date -ud "2020-03-15 19:13" +'%s') - $(date +'%s')))
As of posting, the result is 1744204
Using this website to check, I gets 16 March, not 15 March as expected. Any idea why?
verify the result of your date commands and verify the timezone of both.
The first result of the command shows the timestamp in UTC, and the second one shows the timestamp using the timezone of the system.
Here is the difference:
$ date -ud "2020-03-15 19:13" +'%s'
1584299580
With UTC-3 in my system:
$ date -d "2020-03-15 19:13" +'%s'
1584310380
I hope that help you.
When I issue bash command:
date --date="2018-03-03 12:16:13 -1hour" "+%Y:%m:%d %H:%M:%S"
I expect the result would be:
2018:03:03 11:16:13
but instead, I get:
2018:03:03 15:16:13
I wonder if this has to make with time zones, and how to avoid this behaviour.
I can reproduce this. My timezone is America/New_York
$ date --date="2018-03-03 12:16:13 - 1 hour" "+%Y:%m:%d %H:%M:%S"
2018:03:03 09:16:13
$ env TZ='Europe/Belgrade' date --date="2018-03-03 12:16:13 - 1 hour" "+%Y:%m:%d %H:%M:%S"
2018:03:03 15:16:13
The parser appears to be taking the -1 as the timezone GMT+01:00, then converting that to your local timezone.
If we rearrange the phrases to avoid the timezone parsing ambiguity, we can get your desired result:
$ date --date="- 1 hour 2018-03-03 12:16:13" "+%Y:%m:%d %H:%M:%S"
2018:03:03 11:16:13
From info coreutils 'date invocation'
When a relative item causes the resulting date to cross a boundary where the clocks were adjusted, typically for daylight saving time,
the resulting date and time are adjusted accordingly.
The fuzz in units can cause problems with relative items. For
example, '2003-07-31 -1 month' might evaluate to 2003-07-01, because
2003-06-31 is an invalid date. To determine the previous month more
reliably, you can ask for the month before the 15th of the current
month. For example:
$ date -R
Thu, 31 Jul 2003 13:02:39 -0700
$ date --date='-1 month' +'Last month was %B?'
Last month was July?
$ date --date="$(date +%Y-%m-15) -1 month" +'Last month was %B!'
Last month was June!
Also, take care when manipulating dates around clock changes such
as daylight saving leaps. In a few cases these have added or
subtracted as much as 24 hours from the clock, so it is often wise to
adopt universal time by setting the 'TZ' environment variable to
'UTC0' before embarking on calendrical calculations.
One can avoid that by putting -1 hour before the string,
$ date --date='-1 hour 2018-03-03 12:16:13' "+%Y:%m:%d %H:%M:%S"
2018:03:03 11:16:13
I'm working on a script to automate the download of information from a customer in the period from 00:00 to 23:59 on the same day. To make the correct treatment of the first day of daylight saving time (10/15/2017, in my timezone - BRST), I need to check the timezone of the previous day. However, when I will subtract one day from the first valid time,
date --date="20171015 01:00 -1 day" +%Y-%m-%d
the result is the next day 2017-10-16, not the previous day 2017-10-14. Could anyone help me understand what I might be doing wrong and how should I do this operation in the right way?
I don't really trust GNU date's arithmetic. Instead, I would convert your starting time to seconds since the UNIX epoch, subtract 86400 seconds, and convert the result back to a day. Those conversion routines take daylight saving time into account.
$ TZ=BRST date +%s --date "20171015 01:00"
1508029200
$ TZ=BRST date +%F-%T --date #$((1508029200 - 86400))
2017-10-14-01:00:00
It appears the "BRST" timezone is not very useful: stick to Olson timezone names
$ TZ=BRST date --date="20171015 00:30" "+%F %T"
2017-10-15 00:30:00
$ TZ=America/Sao_Paulo date --date="20171015 00:30" "+%F %T"
date: invalid date ‘20171015 00:30’
I am writing shell where I am going to need dates from last week irrespective of the day I am running on. I tried below but those are somehow failing. Can you please help.
date --date='last Monday'
date --date='last week + last Thursday'
date --date='last week + last Monday'
Thanks
Define on what day your week ends, and then work backwards from there. For example, assuming that your week ends on Sunday, then you can get all the dates from the previous week by doing:
saturday=$(date -d 'last Sunday - 1 day')
friday=$(date -d 'last Sunday - 2 days')
# etc.