Commands using ls (517)

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display a smiling smiley if the command succeeded and a sad smiley if the command failed
you could save the code between if and fi to a shell script named smiley.sh with the first argument as and then do a smiley.sh to see if the command succeeded. a bit needless but who cares ;)

Get your outgoing IP address

Recursively Find Images, Convert to JPEGS and Delete
Simple command to convert a large number of images into jpeg-format. Will delete originals after conversion.

Unlock more space form your hard drive
This command changes the reserved space for privileged process on '/dev/sda' to 1 per cent.

retrieve the source address used to contact a given host
on multihomed hosts, connected to several networks, could be usefull to know the source address (local ip address) used to reach the target host, this command does not require root priviledges. The command use a TCP socket, if there is any error the command return an empty string, elsewhere return a valid ip address.

Continuously listen on a port and respond with a fixed message with netcat (and respond to kill signals)
`while true`: do forever `nc -l -p 4300 -c 'echo hello'`: this is the but anything can go here really `test $? -gt 0 && break`: this checks the return code for ctrl^c or the like and quite the loop, otherwise in order to kill the loop you'd have to get the parent process id and kill it.

Wait for file to stop changing
This loop will finish if a file hasn't changed in the last 10 seconds. . It checks the file's modification timestamp against the clock. If 10 seconds have elapsed without any change to the file, then the loop ends. . This script will give a false positive if there's a 10 second delay between updates, e.g. due to network congestion . How does it work? 'date +%s' gives the current time in seconds 'stat -c %Y' gives the file's last modification time in seconds '$(( ))' is bash's way of doing maths '[ X -lt 10 ]' tests the result is Less Than 10 otherwise sleep for 1 second and repeat . Note: Clever as this script is, inotify is smarter.

Install pip with Proxy
Installs pip packages defining a proxy

Assign function keys to your frequent commands
This is a common use of bind. Hitting any key after will output the key's character sequence. This makes possible using it into a bind command. So pressing ctrl+v and then F2 will output "^[[12~", once binded every time you'll press the function key F2 it will execute your command. Added the \n to make it execute it as well.

Check a server is up. If it isn't mail me.
Alternative to the ping check if your firewall blocks ping. Uses curl to get the landing page silently, or fail with an error code. You can probably do this with wget as well.


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