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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"

Stop long commands wrapping around and over-writing itself in the Bash shell
add the command either in /etc/profile or ~/.bash_profile so that this is available to your shell.

Rotate a video file by 90 degrees CW

Check how far along (in %) your program is in a file
Imagine you've started a long-running process that involves piping data, but you forgot to add the progress-bar option to a command. e.g. $ xz -dc bigdata.xz | complicated-processing-program > summary . This command uses lsof to see how much data xz has read from the file. $ lsof -o0 -o -Fo FILENAME Display offsets (-o), in decimal (-o0), in parseable form (-Fo) This will output something like: . p12607 f3 o0t45187072 . Process id (p), File Descriptor (f), Offset (o) . We stat the file to get its size $ stat -c %s FILENAME . Then we plug the values into awk. Split the line at the letter t: -Ft Define a variable for the file's size: -s=$(stat...) Only work on the offset line: /^o/ . Note this command was tested using the Linux version of lsof. Because it uses lsof's batch option (-F) it may be portable. . Thanks to @unhammer for the brilliant idea.

Uncompress a CSS file
Ever compress a file for the web by replacing all newline characters with nothing so it makes one nice big blob? It is a great idea, however what about when you want to edit that file? ...Serious pain in the butt. I ran into this today in that my only copy of a CSS file was "compressed" with no newlines. I whipped this up and it converted back into nice human readable CSS :-) It could be nicer, but it does the job.

show where symlinks are pointing
displays the output of ls -l without the rest of the crud. pretty simple but useful.

For finding out if something is listening on a port and if so what the daemon is.

Create subversion undo point
Allows you to save progress without committing. To revert to an undo point, svn revert then apply the undo point with patch. $ svn revert -R . && patch -p0 < .undo/2009-03-27_08:08:11rev57 Similar: http://www.commandlinefu.com/commands/view/373/archive-all-files-containing-local-changes-svn

Compare two directory trees.
This uses Bash's "process substitution" feature to compare (using diff) the output of two different process pipelines.

Nicely display permissions in octal format with filename
Nicely display permissions in octal format and filename for a given directory


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