Archive | Scripting

getpass.sh Bash Script

By admin on May 3, 2014 in Bash Scripting

Simple bash script for generating random passwords. We didn’t write this and don’t know exactly where it came from.

#!/bin/bash

MATRIX="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
LENGTH=$1

while [ "${n:=1}" -le "$LENGTH" ]
# ==> Recall that := is "default substitution" operator.
# ==> So, if 'n' has not been initialized, set it to 1.
do
       PASS="$PASS${MATRIX:$(($RANDOM%${#MATRIX})):1}"
       # ==> Very clever, but tricky.

       # ==> Starting from the innermost nesting...
       # ==> ${#MATRIX} returns length of array MATRIX.

       # ==> $RANDOM%${#MATRIX} returns random number between 1
       # ==> and [length of MATRIX] - 1.

       # ==> ${MATRIX:$(($RANDOM%${#MATRIX})):1}
       # ==> returns expansion of MATRIX at random position, by length 1.
       # ==> See {var:pos:len} parameter substitution in Chapter 9.
       # ==> and the associated examples.

       # ==> PASS=... simply pastes this result onto previous PASS (concatenation).

       # ==> To visualize this more clearly, uncomment the following line
       #                 echo "$PASS"
       # ==> to see PASS being built up,
       # ==> one character at a time, each iteration of the loop.

       let n+=1
       # ==> Increment 'n' for next pass.
done

echo -n "$PASS"      # ==> Or, redirect to a file, as desired.

exit 0

#!/bin/bash

MATRIX="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

LENGTH=$1

while [ "${n:=1}" -le "$LENGTH" ]

# ==> Recall that := is "default substitution" operator.

# ==> So, if 'n' has not been initialized, set it to 1.

PASS="$PASS${MATRIX:$(($RANDOM%${#MATRIX})):1}"

# ==> Very clever, but tricky.

# ==> Starting from the innermost nesting...

# ==> ${#MATRIX} returns length of array MATRIX.

# ==> $RANDOM%${#MATRIX} returns random number between 1

# ==> and [length of MATRIX] - 1.

# ==> ${MATRIX:$(($RANDOM%${#MATRIX})):1}

# ==> returns expansion of MATRIX at random position, by length 1.

# ==> See {var:pos:len} parameter substitution in Chapter 9.

# ==> and the associated examples.

# ==> PASS=... simply pastes this result onto previous PASS (concatenation).

# ==> To visualize this more clearly, uncomment the following line

# echo "$PASS"

# ==> to see PASS being built up,

# ==> one character at a time, each iteration of the loop.

let n+=1

# ==> Increment 'n' for next pass.

done

echo -n "$PASS" # ==> Or, redirect to a file, as desired.

exit 0

Apache Watch Script

By admin on May 3, 2014 in Apache, Bash Scripting

Here’s a trivial old script that I sometimes use to monitor for rough processes running on the apache user:

#!/bin/bash

TEST=`ps auxw | grep apache | grep -v "httpd" | grep -v apachewatch | grep -v grep `

if [ "$TEST" != "" ]; then
echo "test";
        echo "Subject: RP apache alert
To: support@reliablepenguin.com

Alert ... something fishy on RP ...

-------
$TEST
-------

" | /usr/sbin/sendmail support@reliablepenguin.com

fi

#!/bin/bash

TEST=`ps auxw | grep apache | grep -v "httpd" | grep -v apachewatch | grep -v grep `

if [ "$TEST" != "" ]; then

echo "test";

echo "Subject: RP apache alert

To: support@reliablepenguin.com

Alert ... something fishy on RP ...

-------

$TEST

-------

" | /usr/sbin/sendmail support@reliablepenguin.com

To Many PHP Session Files

By admin on March 15, 2014 in PHP, Plesk

I seen several servers with high traffic PHP sites hosted on Plesk servers building up an excessive number of PHP session files in /var/lib/php/session. Typically we discover this problem when the server runs out of inodes on the root filesystem.

Plesk provides a cronjob that runs hourly to clean up PHP session files:

/etc/cron.hourly/plesk-php-cleanuper

1	/etc/cron.hourly/plesk-php-cleanuper

For low traffic sites this script work just fine. But for high traffic sites with thousands of sessions per hour the script is too slow and can’t keep up with the rate that files are created.

The problem is the script check each files using the “fuser” utility to determine if the file is in use. This is a slow process. So on these high traffic servers I’ve found it necessary to remove the “fuser” check. Edit /etc/cron.hourly/plesk-php-cleanuper and change this line:

[ -x /usr/lib64/plesk-9.0/maxlifetime ] && [ -d /var/lib/php/session ] && find /var/lib/php/session -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib64/plesk-9.0/maxlifetime) ! -execdir fuser -s {} &nbsp;2>/dev/null \;&nbsp;-delete

1	[ -x /usr/lib64/plesk-9.0/maxlifetime ] && [ -d /var/lib/php/session ] && find /var/lib/php/session -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib64/plesk-9.0/maxlifetime) ! -execdir fuser -s {}  2>/dev/null \; -delete

to:

[ -x /usr/lib64/plesk-9.0/maxlifetime ] && [ -d /var/lib/php/session ] && find /var/lib/php/session -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib64/plesk-9.0/maxlifetime) -delete

1	[ -x /usr/lib64/plesk-9.0/maxlifetime ] && [ -d /var/lib/php/session ] && find /var/lib/php/session -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib64/plesk-9.0/maxlifetime) -delete

Now the session cleanup will run smoothly.

Apache mod_fcgi on CentOS 6.4

By admin on February 6, 2014 in Apache, PHP

There are a lot of tutorials on how to install mod_fcgi with suexec out there but many are incomplete, outdated or just don’t work. One that does work is here:

http://www.howtoforge.com/how-to-set-up-apache2-with-mod_fcgid-and-php5-on-centos-6.2

How-to Cut With Multi-Character Delimiter

By leerb on December 5, 2013 in Bash Scripting

The “cut” command is great for splitting a string on a single character and extracting specific fields. But it will not work with multi-character delimiters. Here’s a simple replacement using awk that will get the job done. Let’s assume you have a string like:

arg1=a&arg2=b&arg3=c

1	arg1=a&arg2=b&arg3=c

We could extract the value of “arg3” using cut with:

echo "arg1=a&arg2=b&arg3=c" | cut -f 3 -d "&" | cut -f 2 -d '='

1	echo "arg1=a&arg2=b&arg3=c" \| cut -f 3 -d "&" \| cut -f 2 -d '='

But this assumes that there are always the same number of proceeding args:

Now lets do it with awk:

awk -F'arg3='  '{print $2}'

1	awk -F'arg3=' '{print $2}'

But what if the args are in different order? The we can use sed:

sed 's/\(.*\)arg3=\(.*\)/\2/g'

1	sed 's/$.$arg3=$.$/\2/g'

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