Commands by iain (3)

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

Optimize PDF documents

Show a 4-way scrollable process tree with full details.
If you want a visual representation of the parent/child relationships between processes, this is one easy way to do it. It's useful in debugging collections of shell scripts, because it provides something like a call traceback. When a shell script breaks, just remember "awwfux".

Quickly analyse an Apache error log
This searches the Apache error_log for each of the 5 most significant Apache error levels, if any are found the date is then cut from the output in order to sort then print the most common occurrence of each error.

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"

Generate Sha1, MD5 hash using echo
This is mostly for my own notes but this command will compute a md5 message digest from the command line. You can also replace md5sum with other checksum commands (e.g., sha1sum)

Encrypt every file in the current directory with 256-bit AES, retaining the original.
The password is stored in the password file, which obviously must be kept secure, encrypted later with gpg, deleted, or whatever you prefer. To decrypt: $ openssl enc -d -aes-256-cbc -salt -in filename.enc -out filename -pass file:/path/to/password-file Alternative ciphers can be used, of course.

Mostly silent FLAC checking (only errors are displayed)
FLAC's built in integrity checks are far more useful then devising a scheme to use MD5 sum files. This will check all the FLAC in a directory and output only errors. Remove the "s" after the "t" and it will be somewhat verbose in the check.

Benchmark SQL Query
Benchmark a SQL query against MySQL Server. The example runs the query 10 times, and you get the average runtime in the output. To ensure that the query does not get cached, use `RESET QUERY CACHE;` on top in the query file.

Automatically find and re-attach to a detached screen session
man screen: "-D -R Attach here and now. In detail this means: If a session is running, then reattach. If necessary detach and logout remotely first. If it was not running create it and notify the user. This is the author?s favorite."

Dump audio from video without re-encoding.
This removes the video and subsequent file size and directly copies the audio.


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: