Shell Programming and Scripting

Hi Dears

kindly I am new here ...I want to ask your help ...

I want to write AWK command when enter date like 20140129 plus 9 then it gives me 20140207 I wrote below but the result was wrong

Code:

#!/bin/ksh

echo "please input the data:"
read a


if echo $a|awk '{if (substr($1,5,1)=="5") {substr($1,6,2)++} else {print "wrong"}}'

Hello shaho87,

Welcome to forums, kindly use code tags for commands/codes/inputs which you are using in your posts, as per forum rules.
Following may help you in same, if you a GNU date in your system.

Code:

date --date="20140129 +9 day"

Thanks,
R. Singh

Hello Ravinder,

kindly , thanks a lot but i want to write script not to use the date.

Hello Shaho87,

Could you please try following and let me know if this helps.

Code:

cat date_script.ksh
echo "Please enter a date in YYYYMMDD format:"
read DATE
echo "Please enter number of days which we want to take date from today's:"
read DAYS
date -d"$DATE +$DAYS day"

Following will be output after running the script.

Code:

./date_script.ksh
Please enter a date in YYYYMMDD format:
20140202
Please enter number of days which we want to take date from today's:
10
Wed Feb 12 00:00:00 EST 2014

Hope this helps.


Thanks,
R. Singh

Hello Ravinder,

kindly,thanks a lot but i want to write a script do the operation manually i mean when we are type date the system directly know it but i want to build mine one thanks million for your helping.

Hello shaho87,

Could you please go through following thread I have given a solution for getting date 1 day ago for NON GNU, kindly take it as a start up and then try frm your end and if you feel any problems please do let us know, we ca assist you.

Date variable - 1 in UNIX


Thanks,
R. Singh

The script that you provided reads a line of data provided by a user into a shell variable named a. It then uses awk to see if the 5th character in the 1st string of non-blank characters is a "5" (presumably the 1st digit in a two digit month is a "5"), and if it is it gets the 6th character from that string, adds 1 to it, and throws it away; otherwise, it prints the string "wrong". In either case, your script then gets a syntax error from the Korn shell because you have an if statement with no matching then nor fi.

Is this a homework assignment?

If it isn't, can you explain (in English) what needs to be done to a string in the format YYYYMMDD to add 9 days to it and end up with a valid date in the same format. If you can't explain what your script needs to do to update your user's input string, you would be much better off using the tools on your system that are designed to perform date arithmetic instead of reinventing the wheel. Even if you can explain the steps required, please explain why you want to reinvent the wheel rather than use system tools that have been written to correctly handle these types of calculations in normal years, in leap years, and (in some cases) even across the conversion from Julian to Gregorian calendars.

And, please tell us what operating system you're using. An operation like this can be performed with a 1988 vintage Korn shell, but some things would be easier with a 1993 or later version of the Korn shell. What version of the Korn shell is installed as /bin/ksh varies from system to system.