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Top Forums Shell Programming and Scripting Find the next day from 20100303 (YYYYMMDD format) Post 302401549 by drewk on Saturday 6th of March 2010 07:27:54 PM
Old 03-06-2010
As stated above, this FAQ will tell you what you need for more complex date and date arithmetic: https://www.unix.com/answers-frequent...rithmetic.html

For this specific problem, you can just use the date command.

If you have the GNU version of date, just use:

Code:
date -d "yesterday" "+%Y%m%d"

If you have BSD, POSIX, Solaris version of date, here is a simple shell script that will do it.

Code:
#!/bin/bash

#call with (basename) 'YYYYMMDD' [+-deltadays]

#there is no error checking, use at your own use...

if [ ! -n "$1" ]
then
  echo "Usage: $(basename $0) YYYYMMDD [+-days]"
  exit $E_BADARGS
fi  

if [ ! -n "$2" ]
then
  	deltadays=-1
  else
	deltadays=$2
fi  


epoch=$(date -j -f "%Y%m%d" $1 "+%s")

(( deltadays *= 60*60*24 ))
(( epoch += deltadays )) 

newday=$(date -j -f "%s" $epoch "+%Y%m%d")

echo $newday

 

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Alien::Package::Rpm(3pm)				User Contributed Perl Documentation				  Alien::Package::Rpm(3pm)

NAME
Alien::Package::Rpm - an object that represents a rpm package DESCRIPTION
This is an object class that represents a rpm package. It is derived from Alien::Package. FIELDS
prefixes Relocatable rpm packages have a prefixes field. METHODS
checkfile Detect rpm files by their extention. install Install a rpm. If RPMINSTALLOPT is set in the environement, the options in it are passed to rpm on its command line. scan Implement the scan method to read a rpm file. unpack Implement the unpack method to unpack a rpm file. This is a little nasty because it has to handle relocatable rpms and has to do a bit of permissions fixing as well. prep Prepare for package building by generating the spec file. cleantree Delete the spec file. build Build a rpm. If RPMBUILDOPT is set in the environement, the options in it are passed to rpm on its command line. An optional parameter, if passed, can be used to specify the program to use to build the rpm. It defaults to rpmbuild. version Set/get version. When retreiving the version, remove any dashes in it. postinst postrm preinst prerm Set/get script fields. When retrieving a value, we have to do some truely sick mangling. Since debian/slackware scripts can be anything -- perl programs or binary files -- and rpm is limited to only shell scripts, we need to encode the files and add a scrap of shell script to make it unextract and run on the fly. When setting a value, we do some mangling too. Rpm maintainer scripts are typically shell scripts, but often lack the leading shebang line. This can confuse dpkg, so add the shebang if it looks like there is no shebang magic already in place. Additionally, it's not uncommon for rpm maintainer scripts to contain bashisms, which can be triggered when they are ran on systems where /bin/sh is not bash. To work around this, the shebang line of the scripts is changed to use bash. Also, if the rpm is relocatable, the script could refer to RPM_INSTALL_PREFIX, which is set by rpm at run time. Deal with this by adding code to the script to set RPM_INSTALL_PREFIX. arch Set/get arch field. When the arch field is set, some sanitizing is done first to convert it to the debian format used internally. When it's retreived it's converted back to rpm form from the internal form. AUTHOR
Joey Hess <joey@kitenet.net> perl v5.14.2 2011-08-05 Alien::Package::Rpm(3pm)
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