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Combines an arbitrary number of transparent png files into one file
This one liner; combines all sequentially numbered files; in this example IMG_0001.png to IMG_1121.png by generating the shell script, making the shell script executable and then running the shell script to combine the 1121 png into a single png file named _final.png tested on Mac OS X 10.6.3 with ImageMagick 6.5.8-0 2009-11-22 Q16 http://www.imagemagick.org

recursively walk down no more than three levels and grab any file with an extension of mp3, mpg, mpeg, or avi

Show sorted list of files with sizes more than 1MB in the current dir
Taken from here: http://linsovet.com/directory-usage-size-sorted-list

Joins args together using the first arg as glue

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.

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" }

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"

rgrep: recursive grep without .svn
Only excludes .svn from filenames.

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"

Use tee + process substitution to split STDOUT to multiple commands
Using process substitution, we can 'trick' tee into sending a command's STDOUT to an arbitrary number of commands. The last command (command4) in this example will get its input from the pipe.


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