Commands by Vasudev (4)

What's this?

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.

Share Your Commands

Check These Out

Enter parameter if empty (script becomes interactive when parameters are missing)
Can be used for command line parameters too. If you have a more complicated way of entering values (validation, GUI, ...), then write a function i.e. EnterValue() that echoes the value and then you can write: $ param=${param:-$(EnterValue)}

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

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

Detect illegal access to kernel space, potentially useful for Meltdown detection
Based on capsule8 agent examples, not rigorously tested

Start a game on the discrete GPU (hybrid graphics)
On laptops featuring hybrid graphics and using the free X drivers, the DRI_PRIME variable indicates which GPU to run on. This alias allows to utilize the faster discrete GPU without installing proprietary drivers.

Fetch the requested virtual domains and their hits from log file
The command will read the apache log file and fetch the virtual host requested and the number of requests.

check open ports without netstat or lsof

Find out my Linux distribution name and version

cd into another dir to run a one-liner, but implicitly drop back to your $OLD_PWD after
Obviously the example given is necessarily simple, but this command not only saves time on the command line (saves you using "cd -" or, worse, having to type a fully qualified path if your command cd's more than once), but is vital in scripts, where I've found the behaviour of "cd -" to be a little broken at times.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: