Question

Ok, so I need to translate a script from a nice linux & bash configuration to ksh in hp-ux. Each and every command expects a different syntax and i want to kill myself. But let s skip the rant.

This is part of my script

anterior=`date +"%Y%0m" -d  1 month ago `

I basically need to get a past date in format 201002. Never mind the thing that, in the new environment, %0m means "no zeroes", while actually in the other one it means "yes, please put that zero on my string". It doesn t even accept the "1 month ago". I ve read the man date for HP-UX and it seems you just can t do date arithmetic with it.

I ve been looking around for a while but all i find are lengthy solutions. I can t quite understand that such a typical administrative task like adding dates needs so much fuss. Isn t there a way to convert my one-liner to, well, i don t know, another one? Come on, i ve seen proposed solutions that used bc, had thirty plus lines and magic number all over the script. The simplest solutions seem to use perl... but i don t know how to modify them, as they re quite arcane.

Thanks!

Answer 1

This is the solution I came to (warning: I m working at a client with draconian security measures, so i don t even have a way to test it, i need to send my scripts to a sysadmin to test them and debug through him).

typeset -Z2 lastmonth
month=`date +%m`
year=`date +%Y`

lastmonth=$((month-1))
if (( month == 1));then
lastmonth=12
year=$((year-1))
fi

Anyway, it strikes me that there is no simpler way to do that.

Answer 2

since yours is simple case of year and month, you could always craft your own date arrays. eg

year=`date +%Y`
month=`date +%m`
anterior=`awk -vm="$month" -vyr="$year"  BEGIN{
  mth["01"]="12"; mth["02"]="01"
  mth["03"]="02"; mth["04"]="03"
  mth["05"]="04"; mth["06"]="05"
  mth["07"]="06"; mth["08"]="07"
  mth["09"]="08"; mth["10"]="09"
  mth["11"]="10"; mth["12"]="11"
  if ( m=="01") { yr-- }
  print yr mth[m]
}  `
echo $anterior

But note that it is only simple and serves to produce only previous 1 month. You can also try the ksh script here

Answer 3

I know this is an old topic, but i had the same problem and this was the solution

Create a shell script, for example, last_month.sh

year=`date +%Y`
month=`date +%m`

month=`expr $month - 1`

if [ $month -eq 0 ]; then
   month=12
   year=`expr $year - 1`
fi

if [ $month -lt 10 ] then
   month="0$month"
fi

echo $year$month
exit 0

then you can call the script and assign to a variable

./last_month.sh | read anterior
echo $anterior

here returns the last month, but you can easily change to accept parameters

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