Commands by gwd (5)

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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"

Remove invalid host keys from ~/.ssh/known_hosts
Useful if you have to tunnel ssh through a local port and it complains of the host key being different. Much easier than manually editing the file.

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

Send email with one or more binary attachments
This command uses mutt to send the mail. You must pipe in a body, otherwise mutt will prompt you for some stuff. If you don't have mutt, it should be dead easy to install.

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

Counting the source code's line numbers C/C++ Java
Count your source and header file's line numbers. This ignores blank lines, C++ style comments, single line C style comments. This will not ignore blank lines with tabs or multiline C style comments.

find an unused unprivileged TCP port
Some commands (such as netcat) have a port option but how can you know which ports are unused?

Get current stable kernel version string from kernel.org
depends on "jq" This is more reliable in my opinion.

Find files with at least one exec bit set

Automatically skip bad songs in your MPD playlist.
Case insensitive. Also you can pull in the songs from a blacklist, one per line - while :; do (mpc current | grep -i -f blacklist.txt && mpc next); sleep 5; done

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