Shell Programming and Scripting

I have shell file that has the following logic, i am new to shell programming.
What does process month $1 do?

I am assuming that the below dates go back three months from sysdate month. is it right :

Code:

curr_month=`date +%Y%m`
Beg_o_time=`date -d "2012/03/01" +%Y%m`
Process_months=$1
Parallel_groups=$2
PROCESS_DIR=/usr/local/bin/TPThadoop

###  Resolve stop time should be one month past
if [ -z $Process_months ]
then
process_end=$Beg_o_time
else
process_end=`date -d "-$Process_months months" +%Y%m`
fi

Thanks a lot for the helpful info.

No, or maybe. It depends on the parameters that you pass to this script when you invoke it. And, of course it also depends on what locale you are using (Is "2012/03/01" March 1st or January 3rd?), what shell you are using (Process_months=$1 is a syntax error in csh and its derivatives, but sets the shell variable Process_months to the string specified by the 1st parameter passed to this script when you invoked it in a shell that uses Bourne shell syntax), and on what operating system you're using (date -d is an unknown option on some system and a means to specify a date and/or time other than the current date and time if you're using date on other operating systems).

Assuming that you are using a shell based on Bourne shell syntax, that you are using an operating system that comes with a GNU version of the date utility, and that you invoke this script with a 1st command line parameter set to 3, then the shell variable process_end will be set to a string that is the complete year number followed by the month number (as a two-digit decimal value with a leading zero if the month represented comes before October) for a date that is three months before you run this script.

Since what you have shown us gives no indication of what will be done with that variable, I have absolutely no idea whether or not that means that the script will process "dates" that "go back three months from sysdate month".

No matter what shell you are using, the test being used in the if statement:

Code:

if [ -z $Process_months ]
then
process_end=$Beg_o_time
else
process_end=`date -d "-$Process_months months" +%Y%m`
fi

is incorrectly specified, but (on a shell using Bourne shell syntax) will accidentally do what was wanted if no command line arguments were specified when the script was invoked. In this case the test will evaluate as true because the string -z is not an empty string while the code seems to have been written to determine whether or not the expansion of the 1st command-line parameter was an empty string which would have been correctly written as:

Code:

[ -z "$Process_months" ]

I hope this helps.