Commands by scw (3)

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Show linux kernel modules dependencies
Use modprobe to list all the dependencies of a certain kernel module. Handy when debugging system issues.

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)
Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

easily convert one unit to another
Easily convert units of similar measurement. May also be invoked alone, units.

Compute the average number of KB per file for each dir
Shorter version using --tag

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"

Get IP from host
I just wanted a simple DNS request. Because host and nslookup commands are not on all systems, we use getent instead. Thanks aulem for that tip.

Identify differences between directories (possibly on different servers)
This can be much faster than downloading one or both trees to a common servers and comparing the files there. After, only those files could be copied down for deeper comparison if needed.

Use bash history with process substitution
Bash has a great history system of its commands accessed by the ! built-in history expansion operator (documented elsewhere on this site or on the web). You can combine the ! operator inside the process redirection

list all opened ports on host

back ssh from firewalled hosts
host B (you) redirects a modem port (62220) to his local ssh. host A is a remote machine (the ones that issues the ssh cmd). once connected port 5497 is in listening mode on host B. host B just do a ssh 127.0.0.1 -p 5497 -l user and reaches the remote host'ssh. This can be used also for vnc and so on.


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