Check These Out
I didn't come up with this myself, but I always add this to my .bash_aliases file. It's essentially the same idea as running "sudo !!" except it's much easier to type. (You can't just alias "sudo !!", it doesn't really work for reasons I don't understand.)
"fc" is a shell built-in for editing and re-running previous commands. The -l flag tells it to display the line rather than edit it, and the -n command tells it to omit the line number. -1 tells it to print the previous line.
For more detail:
$help fc
Check out the usage of 'trap', you may not have seen this one much. This command provides a way to schedule commands at certain times by running them after sleep finishes sleeping. In the example 'sleep 2h' sleeps for 2 hours. What is cool about this command is that it uses the 'trap' builtin bash command to remove the SIGHUP trap that normally exits all processes started by the shell upon logout. The 'trap 1' command then restores the normal SIGHUP behaviour.
It also uses the 'nice -n 19' command which causes the sleep process to be run with minimal CPU.
Further, it runs all the commands within the 2nd parentheses in the background. This is sweet cuz you can fire off as many of these as you want. Very helpful for shell scripts.
Note that the -i will not help in a script. Proper error checking is required.
jq is amazing for manipulating json on the commandline, but the developers have some weird ideas about how to handle shell redirections. This command works around them.
Further reading: https://github.com/stedolan/jq/issues/1110
Shows all block devices in a tree with descruptions of what they are.
Using mplayer's mencoder, you can merge video files together.
'-oac' specifies the audio encoding (here copy, to just copy and not compress)
'-ovc' specifies the video encoding (same thing).
When you run a memory intensive application (VirtualBox, large java application, etc) swap area is used as soon as memory becomes insufficient. After you close the program, the data in swap is not put back on memory and that decreases the responsiveness. Swapoff disables the swap area and forces system to put swap data be placed in memory. Since running without a swap area might be detrimental, swapon should be used to activate swap again.
Both swapoff and swapon require root privileges.
View all files opened by a user in specified directory.
The +D option makes lsof search all sub-directories to complete depth, while ignoring symbolic links.
Save the current directory without having to leave it. When you do decide to leave the current directory, use popd to return to it.
