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Subtracting A month from an arbitrary date in UNIX

 
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# 1  
Old 10-08-2013
Subtracting A month from an arbitrary date in UNIX
Hi,

Is there a way to subtract a month or at least 30 days from an arbitrary or user inputted date without the GNU date?

Example:

please Input date: 2011-05-11

then the answer will be 2011-04-11

This code doesn't work:
Code:
$date -d "2011-05-11 - 1 month" "+%Y%m%d"

Thanks
Last edited by erin00; 10-08-2013 at 02:20 AM..
# 2  
Old 10-08-2013
Doest work will not be much of help...
What output do you get ? ( error message or output...)
What shell are you using and what OS?

That said
Code:
date -d "2011-05-11 - 1 month" "+%Y%m%d"

Will not give your suspected output for it is not what are asking for ( your last format is missing the minus signs...)
it should be
Code:
date -d "2011-05-11 - 1 month" "+%Y-%m-%d"

# 3  
Old 10-08-2013
sorry about the minus sign(-), I just forgot about it.

the error I am receiving is this:

Code:
date: Not a recognized flag: d
Usage: date [-u] [+"Field Descriptors"]

Last edited by Scott; 10-09-2013 at 01:56 AM.. Reason: Code tags
# 4  
Old 10-09-2013
You have not mentionned your shell or most important your OS... it seems that -d is a GNU stuf... so supported by linux, I doubt other OS
Code:
#linux:
has:/home/vbe $ date -d "2011-05-11 - 1 month" "+%Y-%m-%d"
2011-04-11

#    -  BUT --- 
#solaris:
nm1:/export/home/vbe $ uname -r
5.10
nm1:/export/home/vbe $ date -d "2011-05-11 - 1 month" "+%Y-%m-%d"
date: illegal option -- d
usage:  date [-u] mmddHHMM[[cc]yy][.SS]
        date [-u] [+format]
        date -a [-]sss[.fff]
#HP-UX:
ran:/home/vbe $ uname -r
B.11.11
ran:/home/vbe $ date -d "2011-05-11 - 1 month" "+%Y-%m-%d"
date: illegal option -- d
Usage: date [-u] [+format]
       date [-u] [mmddhhmm[[cc]yy]]
       date [-a [-]sss.fff]
#AIX:
n12:/home/vbe $ oslevel
7.1.0.0
n12:/home/vbe $ date -d "2011-05-11 - 1 month" "+%Y-%m-%d"
date: Not a recognized flag: d
Usage: date [-u] [+"Field Descriptors"]

# 5  
Old 10-09-2013
my OS is AIX, I am using korn shell and my perl is v5.12.4
Last edited by erin00; 10-09-2013 at 08:53 PM..
# 6  
Old 10-10-2013
If it's just that - reducing month by one with carry - try this:
Code:
X=2011-05-11
Y=$((${X:5:3}1)); Z=${X:0:4}; [ $Y -le 0 ] && { Y=12; Z=$((Z-1)); }; printf "%s-%02d-%s\n" $Z ${Y} ${X:8}
2011-04-11

# 7  
Old 10-10-2013
I tried it in Cygwin and it worked fine. and this is what I really wanted to happen.

But when I tried it on the putty I got this error:

ksh: ${X:5:3}1: 0403-011 The specified substitution is not valid for this command.
 
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