In awk you can run a command using variables from awk by saving the command to a variable first, then get line can be used to retrieve the result.
/condition/ {
    myVariable = "some value"
    CMDFILE = "echo "myVariable" | head"
    CMDFILE | getline myAnswer
    close(CMDFILE)
    print myAnswer
}

don’t forget the close statement!!,.

Advertisement

Squid by default on RedHat only uses a maximum number of file descriptors of a meagre 1024.
To increase this:

• Add lines in the /etc/security/limits.conf file:
  squid soft nofile 20480
squid hard nofile 20480

• Add line in the /etc/squid/squid.conf file:
  max_filedesc 20480

• Add line in the /etc/init.d/squid file:
  ulimit -HSn 20480

• Restart the squid service:
  service squid restart

This will DEFAULT to the COMPILED setting of 16k file descriptors rather than our selected value of 20K.

Using the file ~/.muttrc you can set the FROM address in outbound messages from the root user to an arbitrary but more appropriate value:
vim ~/.muttrc
Add the lines:

set from=noreply@my.domain
set envelope_from=yes
set realname=NoReply

Or as you see fit – Envelope Sender is also controlled with this setting

To share the same interface when on a Linux server you can use screen
To start a session:
screen -S {session-name}
To join a session:
screen -x {session-name}
Both administrators will then be able to type commands fully visible to each other.

In Vim you can find valid e-mail addresses with the command:
/^[a-z0-9][a-z0-9_\.-]*@[a-z0-9][a-z0-9-]*\(\.[a-z0-9][a-z0-9-]*\)*$
Requires that the e-mail address is on a line on it’s own.
Alternatively:
/[a-z0-9][a-z0-9_\.-]*@[a-z0-9][a-z0-9-]*\(\.[a-z0-9][a-z0-9-]*\)*
Will find such addresses anywhere on a line.

In Vim you can delete empty lines with the command:
:g/^$/d

In Vim you can remove duplicate lines with the command:
:%s/^\(.*\)\n\1$/\1/

Vim can lowercase all lines with the command: ggguG
Similarly to uppercase them use: gggUG

When using TCPDUMP you can use -s 0 to not limit the size of the packets retrieved by the -w {Filename} option.