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Create a false directory structure for testing your commands
This will make a false directory with the same file names as whatever directory you choose. This is wise to use when testing scripts that alter contents, filenames, or move files. I wrote this after an OOPS I made when renaming a directory of JPGs, PNGs, PSDs that were mixed. I recommend this as I lost over 2000 vacation pictures and some graphics I designed for software and web sites. :( NOTE: This only creates name copies, that data itself is not copied.

Use colordiff in side-by-side mode, and with automatic column widths.
Barely worth posting because it is so simple, but I use it literally all the time. I was always frustrated by the limitations that a non-gui environment imposes on diff'ing files. This fixes some of those limitations by colourising the output (you'll have to install colordiff, but it is just a wrapper for diff itself), using side-by-side mode for clearer presentation, and of course, the -W parameter, using tput to automatically insert you terminal width. Note that the double quotes aren't necessary if typed into terminal as-is. I included them for safety sake,

determine if tcp port is open

Install Linux Kernel Headers

Convert seconds into minutes and seconds
This is a very simple way to input a large number of seconds and get a more useful value in minutes and seconds.

list block devices
Shows all block devices in a tree with descruptions of what they are.

Remove newlines from output
?Cat and grep? You can use only grep ("grep \. filename"). Better option is awk.

shuffle lines via perl
Same, without modules... Probably smarter option: just use the shuf command or even sort -R.

Show directories in the PATH, one per line
Shorter version.

Edit 2 or more files in vim using vim -d
Use vim's diff mode to edit two or more files in one window. The '+diffoff!' turns off diff highlighting when the session is started. Use ctrl+w + ctrl+w to switch between windows.


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