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commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

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Grep Recursively Through Single File Extension
Trac 0.12.2-stable

Check if a process is running
Send signal 0 to the process. The return status ($?) can be used to determine if the process is running. 0 if it is, non-zero otherwise.

Convert numbers to SI notation
converts any number on the 'stdin' to SI notation. My version limits to 3 digits of precious (working with 10% resistors).

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

Show File System Hierarchy
Curious about differences between /bin, /usr/bin, and /usr/local/bin? What should be in the /sbin dir? Try this command to find out. Tested against Red Hat & OS X

List all files opened by a particular command
List all file opened by a particular command based on it's command name.

Update program providing a functionality on Debian
On Debian systems, choose which command provides java. Works for all alternatives listed in /etc/alternatives.

Monitor all DNS queries made by Firefox

Find and list users who talk like "lolcats"
Greps IRC logs for phrases and lists users who said them.

Suspend an ssh session.
This must be typed before any other characters have been entered on the line. Use fg, as usual, to resume the ssh session.


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