Shell Programming and Scripting

Hello,

I need a hand please to do with trapping a variable.

Basically I hold todays date in $lDate in form YYYYMMDD (e.g. 20120323)

and I do:

if test -f $impdata/DE${lDate}.ftp
then
DO STUFF!

which works correctly.

However the provider is now giving my an offset date (e.g. yesterday). This really isn't a question about getting yesterday's date as I have found that by using:

PrevDay= expr $lDate - 1

I get 20120322 for this. THe issue that I have is that I was hoping that I could replace my $lDate variable for this with $PrevDate e.g.


if test -f $impdata/DE${PrevDate}SRS.ftp
then
DO STUFF!

However I am not getting anything in PrevDate as it seems to be outputting it to the screen.

As a test I have tried:

PrevDay=123456

echo here1 $PrevDay

PrevDay= expr $lDate - 1 ( if I put $PrevDay here then I get an error)

echo here2 $PrevDay

echo $impdata/DE${PrevDay}.ftp

this gives me the output:

here1 123456
20120322
here2 123456
/ToImport/DE123456.ftp

I'm pretty new to scripting like this, but I assume that I'm using expr incorrectly here, but not sure what and why?

Can anybody help please?

thanks,

Chas

Surround the thing you want to trap in back ticks (`) like so:
variable=`expr $variable + 1`

This will increment $variable by 1

And be aware, that your date calculation will fail every first day of the month...
Have a look at this thread to find some solutions for date calculations.

great guys, thanks for your help

have a nice evening