Commands using gawk (36)

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Run command in an ftp session
By putting ! in front of a command, we are able to run it from an ftp session.

Emergency Alien Invasion Warning
When aliens invade Earth, be first to warn your neighbours by placing your computer screen at a window and executing this potentially Earth-saving command. Ctrl C when aliens are defeated.

small CPU benchmark with PI, bc and time.
$ # 4 cores with 2500 pi digits $ CPUBENCH 4 2500 $. $ every core will use 100% cpu and you can see how fast they calculate it. $ if you do 50000 digitits and more it can take hours or days

convert filenames in current directory to lowercase

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

extract all urls from firefox sessionstore
This will extract all of the urls from a firefox session (including urls in a tab's history). The sessionstore.js file is in ~/.mozilla/firefox/{firefox profile}

Remove a range of lines from a file
Delete a range of line

Remove git branches that do not have a remote tracking branch anymore

Convert CSV to JSON
Replace 'csv_file.csv' with your filename.

Read and write to TCP or UDP sockets with common bash tools
Ever needed to test firewalls but didn't have netcat, telnet or even FTP? Enter /dev/tcp, your new best friend. /dev/tcp/(hostname)/(port) is a bash builtin that bash can use to open connections to TCP and UDP ports. This one-liner opens a connection on a port to a server and lets you read and write to it from the terminal. How it works: First, exec sets up a redirect for /dev/tcp/$server/$port to file descriptor 5. Then, as per some excellent feedback from @flatcap, we launch a redirect from file descriptor 5 to STDOUT and send that to the background (which is what causes the PID to be printed when the commands are run), and then redirect STDIN to file descriptor 5 with the second cat. Finally, when the second cat dies (the connection is closed), we clean up the file descriptor with 'exec 5>&-'. It can be used to test FTP, HTTP, NTP, or can connect to netcat listening on a port (makes for a simple chat client!) Replace /tcp/ with /udp/ to use UDP instead.


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