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list all opened ports on host

Eavesdrop on your system
This command takes a snapshot of the open files for a PID 1234 then waits 10 seconds and takes another snapshot of the same PID, it then displays the difference between each snapshot to give you an insight into what the application is doing.

Using numsum to sum a column of numbers.
if you, like me, do not have the numsum, this way can do the same.

View acceptable client certificate CA names asked for during SSL renegotiations
The key is to use the -prexit option at the command line, and then type "quit" instead of CTRL-C to exit OpenSSL. OpenSSL will then dump its last negotiated state, printing out the contents of the renegotiated handshake. Crucial for debugging client certificate configurations on web servers such as IIS, which renegotiate the SSL/TLS connection with the HTTP request in-flight to ask the client for a cert.

Cheap iftop
Shows updated status in a terminal window for connections to port '80' in a human-friendly form. Use 'watch -n1' to update every second, and 'watch -d' to highlight changes between updates. If you wish for status updates on a port other than '80', always remember to put a space afterwards so that ":80" will not match ":8080".

reapair all mySQL/mariaDB databases
while dumping database if you see following error/warning than you have to repair broken tables/rows

See KeepAlive counters on tcp connections
See connection's tcp timers

Extract raw URLs from a file
you can also use cut instead of awk. less powerful but probably faster. ;)

Time Synchronisation with NTP

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


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