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All what exists in dir B and not in dir A will be copied from dir B to new or existing dir C
Assumed dir A, B, C are subdirs of the current dir Exact syntax of the command is: rsync -v -r --size-only --compare-dest=/path_to_A/A/ /path_to_B/B/ /path_to_C/C/ (do not omit end-slashes, since that would copy only the names and not the contents of subdirs of dir B to dir C) You can replace --size-only with --checksum for more thorough file differences validation Useful switch: -n, --dry-run perform a trial run with no changes made

Show Apt/Dpkg configuration
Shows all configurations to apt and dpkg, rarely changed, you probably still have the default configuration. Go ahead and explore your configuration if you dare, perhaps change your apt-cache directory, Dir::Cache "var/cache/apt/"; or the names of the log files.

Runs previous command but replacing
Replaces the first instance of 'foo' with 'bar'. To replace all instances of 'foo' with 'bar': !!:gs/foo/bar/

check open ports without netstat or lsof

easily strace all your apache *child* processes
Like the original version except it does not include the parent apache process or the grep process and adds "sudo" so it can be run by user.

Extract rpm package name, version and release using some fancy sed regex
This command could seem pretty pointless especially when you can get the same result more easily using the rpm builtin queryformat, like: $ rpm -qa --qf "%{NAME} %{VERSION} %{RELEASE}.%{ARCH}\n" | sort | column -t but nonetheless I've learned that sometimes it can be quite interesting trying to explore alternative ways to accomplish the same task (as Perl folks like to say: There's more than one way to do it!)

test for ksh/bash
Dave Korn gave me this one. It works because ksh allows variable names ( w/o the $name syntax ) used by sh and bash. I wrote it to permit "single source" shell libraries; the current objective: every shell library may be sourced by either shell. see http://github.com/applemcg/backash

create an screenshot, upload it to your server via scp and then open that screenshot in firefox
I often need to send screenshots to other people to explain settings and whatever. So I created this oneline which I use to create the screenshot with imagemagik, upload it via scp to my server and then the command opens an firefox tab with the screenshot. The screenshot can be a region or a window. You just have to replace the parts beginning with YOUR.

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

Set laptop display brightness
An alternative which does not require to be root


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