Shell Programming and Scripting

#!/bin/ksh
# filetimes
minsago()
{
    perl  -e '
          use POSIX qw(strftime);
          $fmt="%c";  # change this to meet your needs
          $now=time;
          $now-=1800;  # 30 minutes = 1800 seconds
         ($sec,$min,$hour,$day,$mon,$yr,$wday,$yday,$dntcare)=localtime($now);
          $result=strftime($fmt, $sec,$min,$hour,$day,$mon,$yr,$wday,$yday,$dntcare);
          print "$result"
         ' $1
}
start=$(minsago)
echo "$start"

DTE=$(date "+%b %d, %Y %r" --date "now -30 minutes")
grep "$DTE" your-file

LC_ALL=C DTE=$(date "+%b %d, %Y %r" --date "now -30 minutes")
grep "$DTE" your-file

$ date "+%b %d, %Y %r" --date "now 30 minutes ago"