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Generate diff of first 500 lines of two files
Useful for massive files where doing a full diff would take too long. This just runs diff on the first 500 lines of each. The use of subshells to feed STDIN is quite a useful construct.

Backup file, create dir and set perms in one shot
Prior to working on/modifying a file, use the 'install -m' command which can both copy files, create directories, and set their permissions at the same time. Useful when you are working in the public_html folder and need to keep the cp'd file hidden.

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

Start a new command in a new screen window
If you are already running screen then you often want to start a command in a fresh window. You use this alias by typing 's whatever' from your command line and 'whatever' starts running in a new window. Good with interactive commands like info, vim, and nethack.

Get the size of all the directories in current directory

Remove a line in a text file. Useful to fix
In this case it's better do to use the dedicated tool

View non-printing characters with cat
Useful to detect number of tabs in an empty line, DOS newline (carriage return + newline). A tool that can help you understand why your parsing is not working.

Cryptographically secure 32-bit RNG in strict ZSH
ZSH ships a couple random number generators via the $RANDOM environment variable and rand48() via zsh/mathfunc, but neither are cryptographically secure. This code produces a 32-bit random number suitable for cryptography. It's only dependency is /dev/urandom and it does not rely on any shell commands or 3rd party utilities. It assumes ZSH was compiled with 64-bit integer support.

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

Know which modules are loaded on an Apache server
This let you know which modules has loaded the Apache server, very useful to know if the mod_rewrite is ready to use.


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