command date script shell bsh/ksh

Question

I need help. I made a shell script that you pass a date earlier than 3 days in YYYYMMDD format and tell me if it is correct or not. My question is. Can i subtract the date command 3 days? thanks.

do you want to use the date command to substract 3 days from the given days? — askmish
– askmish, Commented Aug 3, 2012 at 10:10

Guillaume U · Accepted Answer · 2012-08-03 10:16:38Z

2

you can test :

 DATE="20120803" date -d @$(( `date -d "$DATE" +%s` - (3*24*60*60) ))

answered Aug 3, 2012 at 10:16

Guillaume U

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2 Comments

canredondocity Over a year ago

sorry but ... date: opción no permitida -- d sintaxis: date [-u] ddmmHHMM[[cc]aa][.SS] date [-u] [+format] date -a [-]sss[.fff] date: opción no permitida -- d sintaxis: date [-u] ddmmHHMM[[cc]aa][.SS] date [-u] [+format] date -a [-]sss[.fff]

scai Over a year ago

@canredondocity you shoudn't use the linux tag if your question is not about Linux.

scai · Accepted Answer · 2012-08-03 11:00:58Z

1

for the fancy solution:

INPUT="20120803" INPUT_SECONDS=$(date -d "$INPUT" +%s) THREEDAYSAGO_SECONDS=$(date -d "3 days ago" "+%s") if [ $INPUT_SECONDS -lt $THREEDAYSAGO_SECONDS ]; then echo "too early :(" fi

answered Aug 3, 2012 at 11:00

scai

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2 Comments

canredondocity Over a year ago

date: opción no permitida -- d sintaxis: date [-u] ddmmHHMM[[cc]aa][.SS] date [-u] [+format] date -a [-]sss[.fff] date: opción no permitida -- d sintaxis: date [-u] ddmmHHMM[[cc]aa][.SS] date [-u] [+format] date -a [-]sss[.fff] too early :(

scai Over a year ago

Works here. Please provide meaningful error descriptions including your input.

Community · Accepted Answer · 2017-05-23 12:21:14Z

Although you can use the date command to do this (see Guillame's excellent answer) it may be worth considering a scripting language such as Perl to do more complex stuff more efficiently.

e.g. see this SO answer, using Perl and the DateTime.pm module:

use DateTime; my $date = DateTime->now; $date->subtract(days => 3); print $date->ymd;

@canredondocity This is perl, not a shell script. And you need the DateTime.pm module.

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