42. IPv6 Configuration Lab

43. IPv6 Troubleshooting Lab

44. GRE Tunnel

45. Quality of Service (QoS)

46. VoIP CUCME and Cisco IP Phones

Linux tip of the day🐧

In Linux, the pipe(|) operator is very useful if you want to redirect the output of one command to serve as input to the next for further processing:

$ cat data.txt | grep "No such file"

However, this does not redirect the errors. So, if the file does not exist, the grep command above will not return a match.

What if you want to redirect and process both errors and normal output🤔

This is where this "|&" redirection operator comes in handy.

This operator sends both the standard output (stdout) and standard error (stderr) of the first command over a pipe to the standard input (stdin) of the second command. Take a look at this example:

$ cat data.txt |& grep "No such file"

Notice the difference, the grep command was able to get a match.

The "|&" operator in bash is a shorthand for the "2>&1 |" redirection operator.

$ cmd-1 2>&1 | cmd-2

Quick Linux Tip 🐧

Many people either don’t know about this or rarely use it.

Pressing Ctrl+U in the Linux terminal deletes everything from the cursor position to the beginning of the line.

Similarly, Ctrl+K deletes everything from the cursor position to the end of the line.

This is especially useful if you mistype a password. Instead of holding down the backspace key, simply press Ctrl+U to clear the input and retype the password.

Quick Linux tip 🐧

If you have trouble reading the directories in the $PATH variable, use the tr command to translate colon (":") characters to newline characters ("n") so they can be displayed in lines:

$ echo $PATH | tr ":" "\n"