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Set RGB gamma of secondary monitor
This command first determines whether a second screen is connected. If this is the case, it sets the screen's RGB gamma via xrandr. Useful for cheap or slightly defective monitors with a tint. In this example a yellowing/champagne color deviation is compensated for by decreasing the red and the green portion of the image.

Restart openssh-server on your Synology NAS from commandline.
The correct way to restart openssh-server on your synology nas.

Check if a string is into a variable
Returns true (0) if the string is into $var, or false (1) if not.

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

Recursively execute command on directories (.svn, permissions, etc)
The above command will set the GID bit on all directories named .svn in the current directory recursively. This makes the group ownership of all .svn folders be the group ownership for all files created in that folder, no matter the user. This is useful for me as the subversion working directory on my server is also the live website and needs to be auto committed to subversion every so often via cron as well as worked on by multiple users. Setting the GID bit on the .svn folders makes sure we don't have a mix of .svn metadata created by a slew of different users.

Generate a ZenCart-style MD5 password hash.
ZenCart uses a MD5 with a salt to secure its passwords. If you need to forcibly change someone's password to a known value within the database, this one-liner can generate the password. Change the value of 'p' to the password you want.

Netcat & Tar
Create a tarball on the client and send it across the network with netcat on port 1234 where its extracted on the server in the current directory.

Reuse all parameter of the previous command line
!* is all of the arguments to the previous command rather than just the last one. This is useful in many situations. Here's a simple example: $ vi cd /stuff oops! [exit vi, twice] $ !* expands to: cd /stuff

Execute matlab sentences from command line
Execute matlab sentences in shell script: for var in `seq 0 0.2 1` ; do echo "my_function($var);" | matlab -nodisplay done

One liner to parse all epubs in a directory and use the calibre ebook-convert utility to convert them to mobi format
all ebook-convert -options are optional. all you really need to pass ebook-convert is the incoming and outgoing names, with extensions. Has been tested on Ubuntu 10.10


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