Commands by prabhakaran9397 (2)

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

Short one line while loop that outputs parameterized content from one file to another

One-liner to generate Self-Signed SSL Certificate+Key without any annoying prompts or CSRs
Handy if you want to quickly generate a self-signed certificate. Also can be used in your automated scripts for generating quick-use certificates.

copy root to new device
Clone a root partition. The reason for double-mounting the root device is to avoid any filesystem overlay issues. This is particularly important for /dev. Also, note the importance of the trailing slashes on the paths when using rsync (search the man page for "slash" for more details). rsync and bash add several subtle nuances to path handling; using trailing slashes will effectively mean "clone this directory", even when run multiple times. For example: run once to get an initial copy, and then run again in single user mode just before rebooting into the new disk. Using file globs (which miss dot-files) or leaving off the trailing slash with rsync (which will create /mnt/target/root) are traps that are easy to fall into.

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" }

Time conversion/format using the date command

Close a hanging ssh session
~ is the ssh control character. If you type it after a newline, you can example force close the ssh session. , ~, then . If you want more info, type ~? when you are connecting using ssh. Very useful to kill of any hanging ssh sessions when nothing else works.

Search some text from all files inside a directory

Import/clone a Subversion repo to a git repo

Step#2 Create a copy of the bootload and partition table!
Step#2 Create a copy of the bootload and partition table!

find packages installed from e.g. sid which are newer than those available from e.g. testing when sid is no longer present as a source repo
This is useful if you add sid, install some packages, then remove sid and want to work out which packages you installed from sid that should be removed (e.g. before an upgrade to the new stable). Alternatively you can think of this as "find installed packages that can no longer be installed."


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: