Getting IP and MAC Address from BASH/Shell Script

Ever wondered how to get your IP address and MAC address and then use it in a Linux shell script? Here’s how:

#!/bin/sh
# showIPandMAC.sh

IP=$(ip addr show wlan0 | awk '/inet / {print $2}' | cut -d/ -f 1)
MAC=$(ip link show wlan0 | awk '/ether/ {print $2}')

echo "IP Address: $IP"
echo "MAC Address: $MAC"

# EndOfFile

You can change the wlan0 into whatever device you have, e.g. eth0.

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Looping Through Files with Spaces and Special Characters in BASH

This is useful for batch processing of files with special characters such as space, ampersand (&), underscore, etc. The example below is to do mass conversion of mp4 files I downloaded from youtube into mp3 files.

Instead of giving the command directly, I prefer always to “echo” the command so I can see whether it’s giving the desired batch command or not. If all okay, then remove the echo.

$ find ./ -type f | sed 's/.mp4//' | sed 's/\.\///' | while read FILE;
do
echo ffmpeg -i \"$FILE.mp4\" -ab 192k \"$FILE.mp3\";
done

But the with the above script, somehow ffmpeg won’t accept the filenames – although I already put quote in both end. Strange enough, if I give the command directly for example:
$ ffmpeg -i "Some file (3_11)_.mp4"
It works.

Let’s just focus on getting the job done shall we? The easiest workaround is by redirecting the output of the script above into a file by putting
> batch.sh
in the end of the script (right after “done”). So the batch file will look like this:

ffmpeg -i "Chaka Khan _ I'm Every Woman _(360p_H.264-AAC).mp4" -ab 192k "Chaka Khan _ I'm Every Woman _(360p_H.264-AAC).mp3"
ffmpeg -i "David Foster _ Winter Games _(360p_H.264-AAC).mp4" -ab 192k "David Foster _ Winter Games _(360p_H.264-AAC).mp3"
ffmpeg -i "Earth, Wind & Fire (3_11) - Fantasy(360p_H.264-AAC).mp4" -ab 192k "Earth, Wind & Fire (3_11) - Fantasy(360p_H.264-AAC).mp3"
ffmpeg -i "Earth, Wind & Fire (4_11) - Sing a song(360p_H.264-AAC).mp4" -ab 192k "Earth, Wind & Fire (4_11) - Sing a song(360p_H.264-AAC).mp3"

Then make the file executable
$ chmod +x batch.sh
and run it
$ ./batch.sh