Commenting multiple lines in a shell script using vi/vim in a single step

A text editor like vi or vim can be used to comment multiple lines in a shell script (or any other scrip or configuration file) in a single go rather than adding # or whatever that goes for a comment for the script in question.

Open the file to be edited using vi/vim using the command vi filename (where filename can be replaced by the name of the file), now enter the command mode by pressing : .In order to comment multiple lines ( i.e. to add a # to the beginning of the line) , say lines from 5 to 10 in the script, type the command
:5,10s/^/#/ # : in the command is part of entering the editing/ex mode in vi.

Note# The command :set nu can be used to view line numbers in vi/vim
Clarification
General Syntax
==============================================
:%s/r1/r2/ is the syntax used for string substitution in vi/vim
Syntax split
: Enter command mode
% Perform the command on all lines
s Short form for :substitute command
r1 Can be replaced with any string in the script/file that is to be replaced
r2 Can be replaced with any string which should replace the string r1 in the script/file
/ Used a separator
Changes from syntax in executed command
============================================

In the command that we used for substitution/adding comments to lines starting from 5 to 10
% has been replaced with 5,10 so that the command will be executed only for lines starting from 5 to 10
^ caret [^ ] matches the position before the first character in the string (hence in the command that we executed the substitution takes place for the position before the first character[=r1])
# Replacement for r2 in syntax (i.e. # is used as the character/string which substitutes r1[position before the first character])

Comment removal

In order to uncomment multiple lines (we will remove # from the lines that we have commented, i.e. from 5 to 10) we can use the command
:5,10s/^#//
Clarification
^# Matches all characters starting with # (since ^ means position before the first character, ^x [x can be replaced with any character which does not hold a special meaning in bash, or \x if x has got a special meaning] will match any line which has got x as the character at the first character)
// Two /s without any in between space :: hence substitution will completely remove # from the beginning without adding anything
Commenting all lines in a script/file
Open the file in vi/vim and use the command
:%s/^/#/g

g stands for global (so that the substitution will occur globally, i.e. for all lines in the script)
All the rest have already been explained in General Syntax
Note: For php files which treat ; as the commenting character instead of # , # can be replaced with ; i.e. for commenting all lines in a php file we can use the command %s/^/;/g

Tracked?

Privacy is everybody main concern especially while using the internet. Would you like to be tracked? Everyone would have the answer NO. Therefore, here is a solution in the form of a plugin/add-on. Best of all; it is FREE. Its compatible with Windows, Linux and even Mac. Currently it is available for the browsers: Chrome, Firefox, Safari, and Internet Explorer. The number of companies that are tracking you would surprise you. You would no longer have to worry about the ever-changing piracy policies.

Check out this video:

You can download it from here

Article Authored by Rosemary J Thomas
Author, Rosemary J Thomas, is the Business Development Executive with SupportPRO.
SupportPRO offers 24X7 technical support services to Web hosting companies and service providers.

Re-Route SMTP Via IP Tables

Consider a situation where the email server ip gets blacklisted in a server with any email server like exim or qmail, we can reroute the smtp via another IP using IP Tables.

For routing the SMTP via xxx.xxx.xx.xx, issue the following command:

iptables -t nat -A POSTROUTING -o eth0 -p tcp dport 25 -j SNAT to xxx.xxx.xx.xx

How to install nginx with upload-progress-module in the server?

You can install nginx with upload progress-module. You can follow the bellow steps to install.

1. cd /usr/local/src
2. wget http://nginx.org/download/nginx-0.8.53.tar.gz
(download from http://github.com/masterzen/nginx-upload-progress-module and sftp to “/usr/local/src”) masterzen-nginx-upload-progress-module-v0.8.1-0-gc740674.tar.gz
3. tar xzvf nginx-0.8.53.tar.gz
tar xzvf masterzen-nginx-upload-progress-module-v0.8.1-0-gc740674.tar.gz

4. cd nginx-0.8.53

./configure –prefix=/opt \
–sbin-path=/opt/sbin/nginx \
–conf-path=/opt/etc/nginx/http-nginx.conf \
–error-log-path=/var/log/http-nginx/error.log \
–http-log-path=/var/log/http-nginx/access.log \
–pid-path=/var/run/http-nginx.pid \
–lock-path=/var/lock/http-nginx.lock \
–user=www-data \
–group=www-data \
–with-http_realip_module \
–with-rtsig_module \
–with-http_gzip_static_module \
–with-http_stub_status_module \
–with-http_ssl_module \
–without-mail_pop3_module \
–without-mail_imap_module \
–without-mail_smtp_module \
–add-module=/usr/local/src/masterzen-nginx-upload-progress-module-c740674/

5. make
6. make install

You can control nginx from /etc/init.d/nginx <start/stop/restart> and the conf file by default is /etc/nginx/nginx.conf .