convert standard timestampt to epoch format using awk/nawk on Solaris

Question

I need to convert some timestamp on Solaris to epoch format without any GNU installed.

I gave it a try with below code. However, sometime the return value has 1-2 days deviated from the correct value

echo "Mar 20 20:09" | nawk -v FS="[: ]+" 'BEGIN {
    month_array["Jan"]="01";
    month_array["Feb"]="02";
    month_array["Mar"]="03";
    month_array["Apr"]="04";
    month_array["May"]="05";
    month_array["Jun"]="06";
    month_array["Jul"]="07";
    month_array["Aug"]="08";
    month_array["Sep"]="09";
    month_array["Oct"]="10";
    month_array["Nov"]="11";
    month_array["Dec"]="12";
}
{
    year=2016;
    month=month_array[$1];
    day=$2; hour=$3; minute=$4;
    if (month > 2) {
        month=month+1;
    } else {
        month=month+13; year=year-1;
    }

    day=(year*365)+(year/4)-(year/100)+(year/400)+(month*306001/10000)+day;
    days_since_epoch=day-719591;
    seconds_since_epoch=(days_since_epoch*86400)+(hour*3600)+(minute*60);
    printf "%d\n", seconds_since_epoch;
}'
1458677340

bash-3.2$ ctime 1458677340
Tue Mar 22 20:09:00 2016

Thanks so much

Answer 1

Assuming all month have 30.6 days is obviously doomed.

Here are two ways to do what you want to achieve under Solaris.

Using touch and truss (for the fun):

$ touch -t "03202009" file
$ truss -f -v 'lstat,lstat64' ls -d file 2>&1 | nawk '/mt =/ {printf "%d\n",$10}'
1458504540
$ ctime 1458504540
2016/03/20, 20:09:00

Using perl:

$ touch -t "03202009" file
$ perl -sle '@stat=stat($filename); print "$stat[8]"' -- -filename=file
1458504540