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Add directory to $PATH if it's not already there
Sometimes in a script you want to make sure that a directory is in the path, and add it in if it's not already there. In this example, $dir contains the new directory you want to add to the path if it's not already present. There are multiple ways to do this, but this one is a nice clean shell-internal approach. I based it on http://stackoverflow.com/a/1397020. You can also do it using tr to separate the path into lines and grep -x to look for exact matches, like this: $ if ! $(echo "$PATH" | tr ":" "\n" | grep -qx "$dir") ; then PATH=$PATH:$dir ; fi which I got from http://stackoverflow.com/a/5048977. Or replace the "echo | tr" part with a shell parameter expansion, like $ if ! $(echo "${PATH//:/$'\n'}" | grep -qx "$dir") ; then PATH=$PATH:$dir ; fi which I got from http://www.commandlinefu.com/commands/view/3209/. There are also other more regex-y ways to do it, but I find the ones listed here easiest to follow. Note some of this is specific to the bash shell.

Find default gateway (proper at ppp connections too)

archlinux: shows list of packages that are no longer needed
Shows a list of packages which are no longer needed as dependencies of any package installed on your system.

Get IPv4 of eth0 for use with scripts
I've been using it in a script to build from scratch proxy servers.

Batch Convert SVG to PNG (in parallel)
Convert some SVG files into PNG using ImageMagick's convert command. Run the conversions in parallel to save time. This is safer than robinro's forkbomb approach :-) xargs runs four processes at a time -P4

Chrome sucks

Find the package that installed a command

convert wav into mp3 using lame

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

ANSI 256 Color Test
Terminal Color tester using python, works with py2 and 3


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