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Alert visually until any key is pressed
I learned a few things reading this command. But I did run into a few issues: 1. On systems that don't use GNU echo (e.g. macOS 10.14.5 Mojave), the e option may not be supported. In this case ANSI escape codes will echoed as text and the terminal will not flash, like this: \e[?5h\e[38;5;1m A L E R T Thu Jun 20 16:31:29 PDT 2019 2. Since the read command strips\ignores leading backslashes, if a user types the backslash character once in the loop, it will not break. Typing backslash twice in a loop will break as expected. 3. The foreground color is set to red (\e[38;5;1m) on every loop. This could be set once before we call while, and then reset once when the loop breaks. 4. Instead of resetting the foreground color when it breaks, the video mode is set back to normal (\e[?5l). This has the effect of leaving the terminal text red until it is manually reset. The alternative I'm proposing here addresses these issues. I tested it on macOS and Arch Linux.

convert uppercase files to lowercase files

Rename files in batch

Find number of computers in domain, OU, etc .

Setup a persistant SSH tunnel w/ pre-shared key authentication
This creates a persistent ssh -i /path/to/key -ND local-IP:PORT User@Server connection. You may have to install autossh. -f puts in daemon mode. if you are having trouble, try it without -f.

Makes the permissions of file2 the same as file1
same as the chmod example, but should also copy extended access control list attributes. deliberately stolen from: $man setfacl

Know SELinux status
Usefule to check whether SELinux is in force or disabled. Though you need to be superuser while execute this command.

Convert your favorite image in xpm for using in grub
* size must be 640?480 pixels * only has 14 colors * save it in XPM format Edit /boot/grub/menu.lst and add splashimage=(hd0,0)/boot/grub/grubimg.xpm make sure for your path name and hard disk

Preserve user variables when running commands with sudo.
In this case the current user has proxy variable set which allows access to the rpm on the internet but needs root privs to install it. Running sudo -E preserves the current user proxy var and allows the rpm install to be executed with sudo.

Check whether IPv6 is enabled
Checks whether IPv6 is enabled system-wide by reading from procfs.


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