Binary Expressions

Background Knowledge

Since MySQL v4.1 timestamp and datetime data types are formatted “YYYY-MM-DD HH:MM:SS”. Prior to MySQL v4.1 the timestamp was formatted as YYYYMMDDHHMMSS” and datetime formatted as “YYYY-MM-DD HH:MM:SS”. Refer to MySQL Reference Manual for further details.

The Unix timestamp differs from MySQL. Unix’s timestamp is a integer value of seconds since January 1, 1970. For further explanation of Unix timestamps refer to Wikiepedia or UnixTimestamp.com.

Solutions

In MySQL you can use Unix_Timestamp() function.

Query Example: SELECT Unix_Timestamp(Date_Entered) FROM Foo;

Using PHP you can use strtotime() function.

PHP Example: $nUnixTimestamp = strtotime($nTimestamp);

Background Knowledge

This case was done on a machine running OpenBSD i386 v3.7 operating system with Perl v5.8.6 built for i386-openbsd using BASH as the command prompt interrupter.

I’ll be honest I have very little knowledge of Perl so if you have anything to comment on or suggest please do so.

Problem

I tried to install a couple Perl modules and received an error message of “Out of Memory!”.

Solution

Just to clarify I have very little knowledge when it comes to Perl, so this solution may or may not work for you.

On Unix machines each user has a ulimit or “user limit” which is basically from what I understand sets the limit for each resource to ensure the system is not over loaded or abused. In this case at least for me, my issue was not having a big enough data seg size. Type at the command prompt without quotes “ulimit -a” to see a list of the set limits. I increased my data seg size from 76800 to 200000. I did this by typing at the command prompt without quotes, “ulimit -d 200000″.

You may need to play with this value for your case or other ulimits. Don’t worry about the changes as none of them are permanent in this case, at least to my knowledge. When you use the ulimit it only changes it for the user you are using and for that given session. If you require more permanent changes look into using ulimit in the login script or better yet change your system configuration settings.

Comments/Thanks

Many thanks to Scott Corley who posted an excellent blog entry entitled “perl Out of memory! (with solution)” on his blog called “Red Mercury Labs”. Without this I was getting know where fast.

If anyone can provide some further knowledge on ulimit it would be much appreciated.

Source: Red Mercury Labs - perl Out of memory! (with solution)

I have learned by using the “find”, “wc” and “awk” commands one can find the total number of lines within files of a given directory and sub-directories. Thanks to NicM on IRC server Freenode channel #OpenBSD for his solution below.

Solution
find /path/blah -type f -name ‘*.php’|while read i; do wc -l <$i; done|awk ‘BEGIN { x=0 }; { x+=$1 }; END { print x }’

Note: Shell must be bourne-compatible.

I will go through a basic setup of Sendmail as a smart host. The goal is to relay all mail outgoing from an internal OpenBSD server to a gateway that will then send out the email on the server’s behalf. No inbound email traffic is permitted to the internal OpenBSD server only the outside world sees the gateway as the mail server. I’m by no means a Sendmail expert, the steps I explain here is what I’ve learned on my own and with the assistance of dhartmei and NicM in IRC EFNet #OpenBSD channel and cannonball in IRC Freenode #sendmail channel.

Setup

• Make a copy of openbsd-localhost.mc, “cp usr/share/sendmail/cf/openbsd-localhost.mc /usr/share/sendmail/cf/openbsd-localhost-smarthost.mc”.
• Edit openbsd-localhost-smarthost.mc and add this statement without double quotes “include(`/usr/share/sendmail/m4/cf.m4′)dnl”.
• Edit openbsd-localhost-smarthost.mc and add this statement without double quotes “define(`SMART_HOST’,`input_host_here’)dnl”. Note: if an IP address is used enclose the IP address with square brackets.
• Compile configuration file without double quotes, “sudo m4 /usr/share/sendmail/cf/openbsd-localhost-smarthost.mc > /etc/mail/localhost.cf”. If you receieve “permission denied”, try this instead “sudo ksh -c ‘m4 /usr/share/sendmail/cf/openbsd-localhost-smarthost.mc > /etc/mail/localhost.cf’”.
• Shutdown Sendmail (kill). Without double quotes do “sudo kill ‘head -n1 /var/run/sendmail.pid’”.
• Start Sendmail as started previously, “sendmail -L sm-mta -C/etc/mail/localhost.cf -bd -q30m”. You can see how sendmail was started by executing without double quotes “grep sendmail /etc/rc.conf*”. In my case it returned /etc/rc.conf:sendmail_flags=”-L sm-mta -C/etc/mail/localhost.cf -bd -q30m”.

openbsd-localhost-smarthost.mc example

divert(-1)
#
# Copyright (c) 1998 Sendmail, Inc.  All rights reserved.
# Copyright (c) 1983 Eric P. Allman.  All rights reserved.
# Copyright (c) 1988, 1993
#       The Regents of the University of California.  All rights reserved.
#
# By using this file, you agree to the terms and conditions set
# forth in the LICENSE file which can be found at the top level of
# the sendmail distribution.
#
#

#
#  This configuration only runs sendmail on the localhost interface.
#  This allows mail on the local host to work without accepting
#  connections from the net at large.
#

divert(0)dnl
include(`/usr/share/sendmail/m4/cf.m4')dnl
VERSIONID(`@(#)openbsd-localhost-smarthost.mc $Revision: 1.4 $')
OSTYPE(openbsd)dnl
FEATURE(nouucp, `reject')dnl
FEATURE(`accept_unresolvable_domains')dnl
FEATURE(`no_default_msa')dnl
define(`SMART_HOST',`[10.10.8.1]')dnl
MAILER(local)dnl
MAILER(smtp)dnl
DAEMON_OPTIONS(`Family=inet, address=127.0.0.1, Name=MTA')dnl
DAEMON_OPTIONS(`Family=inet6, address=::1, Name=MTA6, M=O')dnl
DAEMON_OPTIONS(`Family=inet, address=127.0.0.1, Port=587, Name=MSA, M=E')dnl
DAEMON_OPTIONS(`Family=inet6, address=::1, Port=587, Name=MSA6, M=O, M=E')dnl
CLIENT_OPTIONS(`Family=inet6, Address=::')dnl
CLIENT_OPTIONS(`Family=inet, Address=0.0.0.0')dnl
dnl
dnl Some broken nameservers will return SERVFAIL (a temporary failure)
dnl on T_AAAA (IPv6) lookups.
define(`confBIND_OPTS', `WorkAroundBrokenAAAA')dnl

Changing the name/IP address of the server is quite simple. Using your favorite text editor editing the following files and change all reference to server name and server IP address.

• /etc/hosts
• /etc/hosts.allow
• /etc/hosts.deny
• /etc/mygate
• /etc/myname
• /etc/hostname.*
• /etc/resolv.conf
• /etc/nttpd.conf
• /var/www/conf/httpd.conf

At the command prompt run the following command to reconfigure your NIC with the new IP address and applicable netmask.

ifconfig le1 inet IP_ADDRESS_HERE netmask NETMASK_HERE

The “le1″ is the device name of the NIC. Not sure what the NIC device name is? At the console prompt type without quotes “ifconfig -a” and locate the network card device name.

Source: OpenBSD FAQ - Networking