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Make a directory named with the current date
Create a directory named with the current date in ISO 8601 format (yyyy-mm-dd). Useful for storing backups by date. The --iso switch may only work with GNU date, can use format string argument for other date versions.

Remove orphaned dependencies on Arch
-Qdt Lists dependencies/packages which are no longer required by any packages -q Output only package name (not the version number) -R Remove package(s) Rest is self-explanatory. I just started out with Arch - so if there is any better/standard method to achieve the same - please suggest.

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

Get the version of sshd on a remote system
I used this to confirm an upgrade to an SSH daemon was successful

Boooted as EFI/UEFI or BIOS

Diff remote webpages using wget

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Base conversions with bc
Easily convert numbers to their representations in different bases. Passing "ibase=16; obase=8; F2A" to bc will convert F2A (3882 in decimal) from Hex to Octal, and so on.

move cursor to beginning of command line
Pressing Ctrl combined with 'a' will move the cursor to the beginning of the command under bash (other shells?). I used to do this after arrowing up for the last command, then typing 'sudo ' to run the last command as root, but of course the all time greatest command here `sudo !!` is more succinct. Still Ctrl+A can be very useful when you want to edit something at/close to the beginning of the command line.

Execute a command at a given time


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