Use the shell to get the date n days before the specified date _linux shell

First, create test files test.sh

#!/bin/sh
./etc/profile

# Parameters:
# Args[0], data date, date format Yyyy-mm-dd
# Take 30 days before the date

function Get_date_ 30daysbefore ()
{
 sec= ' date-d $ +%s '
 sec_30daysbefore=$ ((sec-86400*30))
 days_before= ' date-d @$ Sec_30daysbefore +%f '
 echo $days _before
}

If [$# = 1]; then today=$1 dates_30=
 ' Get_date_ 30daysbefore '
else
 today= ' date-d -1days ' +%y-%m-%d ' dates_30= ' date-d
 -30days
' +%y-%m-%d ' Fi

echo $today
echo $dates _30

Ii. Non-parametric operation

# # without parameters, starting from the current time
$./test.sh

2016-10-28
2016-09-29

Third, the transfer of the parameters of the operation

$./test.sh 2015-10-29
2015-10-29
2015-09-29

Summarize

The above is the use of shell to get the specified date of the date of the full content of N days, I hope the content of this article for everyone's study or work can help, if there is doubt you can message exchange.