Re: A couple of scripting queries

From: Tony Lawrence (foo_at_pcunix.com)
Date: 03/24/05

  • Next message: Tony Lawrence: "Re: A couple of scripting queries" 
    Date: Thu, 24 Mar 2005 14:11:57 -0500

    Simon Hobson wrote:
    > I've been writing a script at work, mostly using Informix to extract some
    > data from the sales system - and I've come up with a couple of problems that
    > are new to me. Yes I'm sure they are bot a doddle in Perl - but I haven't
    > learned Perl (yet). This all runs in sh, not ksh, and will be executed
    > (indirectly) from cron.
    >
    >
    >
    > 1) 'double substitution' of variables
    >
    > I need to repeat the same operation for the next 11 months, so I calculated
    > the start and end dates and stored them in variables S1 to S11 and E1 to E11
    > - thinking that I could then do something along the lines of :
    >
    > for month in 1 2 3 4 5 6 7 8 9 10 11
    > do
    > echo "select <something> from <something>
    > where date_required between \"${Sn}\" and \"${En}\" " \
    > | dbaccess data -
    > done
    >
    > But then I realised that ${S${month}} doesn't work !
    >
    > In the end I did this :
    >
    > for month in 1 2 3 4 5 6 7 8 9 10 11
    > do
    > start=`echo 'echo "${S'${month}'}"' | /bin/sh`
    > end=`echo 'echo "${E'${month}'}"' | /bin/sh`
    > echo "select <something> from <something>
    > where date_required between \"${start}\" and \"${end}\" " \
    > | dbaccess data -
    > done
    >
    > I'm sure there must be a better way than start=`echo 'echo "${S'${month}'}"'
    > | /bin/sh` to do this - any ideas ?
    >
    >
    >
    > 2) date calculations
    >
    > I suspect some of you might have seen this part coming ...
    >
    > In the general case I need to process a whole pile of stuff for yesterdays
    > date (because the script will be run early in the morning). So I need to get
    > yesterdays date, and then the start and end dates for that month and the
    > following 11 months.
    >
    > At the moment I've done this with a combination of some rather unpretty
    > script and informix scripts (which I'm too embarassed to quite here). Again
    > I'm sure there'll be a better way of doing it - any ideas ?
    >
    >
    >
    > TIA, Simon
    >

    You can get yesterday's date as simply as

    date --date='1 day ago'

    If you want more complicated things, it's harder to do in the shell (and
    usually no reason to); see http://aplawrence.com/Unix/yesterday.html and
    for an example of doing it in perl see
    http://aplawrence.com/Unix/perlnetftp.html 

    -- 
Tony Lawrence
Unix/Linux/Mac OS X  resources: http://aplawrence.com
  • Next message: Tony Lawrence: "Re: A couple of scripting queries"

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