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Full Discussion: Adding days to date
Top Forums Shell Programming and Scripting Adding days to date Post 302971594 by Don Cragun on Friday 22nd of April 2016 06:50:17 AM
Old 04-22-2016
You haven't told us what OS you're using and you haven't told us what shell you're using. If you had the GNU date utility, you could use date -d in a shell script (but you have said that is not an option). If you have a recent version of ksh, you could use:
Code:
x=10
printf '%(%Y-%m-%d)T\n' "now + $x days"

currently producing the output:
Code:
2016-05-02

Of course, it is easy just using a standard date utility, parameter expansions, and arithmetic expansions to get the current date, extract the current day of the month, add the desired number of days you want to go forward and reformat the day of the month in the date output you want as long as the resulting day number is no greater than 28.

Otherwise, if you're unwilling to use perl, you can use date to get the current date and build calendar logic into your shell script, or use date to get the current date and process output from cal to find the date x days later (or earlier).
 

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LEARN ABOUT CENTOS

cal

CAL(1)								   User Commands							    CAL(1)

NAME

       cal - display a calendar

SYNOPSIS

       cal [options] [[[day] month] year]

DESCRIPTION

       cal displays a simple calendar.	If no arguments are specified, the current month is displayed.

OPTIONS

       -1, --one
	      Display single month output.  (This is the default.)

       -3, --three
	      Display prev/current/next month output.

       -s, --sunday
	      Display Sunday as the first day of the week.

       -m, --monday
	      Display Monday as the first day of the week.

       -j, --julian
	      Display Julian dates (days one-based, numbered from January 1).

       -y, --year
	      Display a calendar for the current year.

       -V, --version
	      Display version information and exit.

       -h, --help
	      Display help screen and exit.

PARAMETERS

       A single parameter specifies the year (1 - 9999) to be displayed; note the year must be fully specified: cal 89 will not display a calendar
       for 1989.

       Two parameters denote the month (1 - 12) and year.

       Three parameters denote the day (1-31), month and year, and the day will be highlighted if the calendar is displayed on a terminal.  If	no
       parameters are specified, the current month's calendar is displayed.

       A year starts on Jan 1. The first day of the week is determined by the locale.

       The Gregorian Reformation is assumed to have occurred in 1752 on the 3rd of September. By this time, most countries had recognized the ref-
       ormation (although a few did not recognize it until the early 1900's). Ten days following that date were eliminated by the reformation,	so
       the calendar for that month is a bit unusual.

HISTORY

       A cal command appeared in Version 6 AT&T UNIX.

AVAILABILITY

       The cal command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux							     June 2011								    CAL(1)
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