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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.

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Binary clock

Compare a remote dir with a local dir
You can compare directories on two different remote hosts as well: $ diff -y

Batch convert PNG to JPEG
Convert all PNG images in directory to JPEG using ImageMagick, and delete the old PNG images.

GIT: list unpushed commits

memcache affinity: queries local memcached for stats, calculates hit/get ratio and prints it out.
queries local memcached for stats, calculates hit/get ratio and prints it out.

Is it a terminal?
Oddly, the isatty(3) glibc C call doesn't have a direct analogue as a command 'isatty(1)'. All is not lost as you can use test(1). For example, your script might be run from a tty or from a GUI menu item but it needs to get user-input or give feedback. Now your script can test STDIN with 'isatty 0' or STDOUT with 'isatty 1' and use xmessage(1) if the tty is not available. The other way to test for this is with 'tty -s' - but that's only for STDIN.

Get line number 12 (or n) from a file
Extracts only file number 12 from file. It's meant for text files. Replace 12 with the number you want. First line starts at 1 not 0. We use q on next line so doesn't process any line more.

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"

Display a block of text: multi-line grep with perl
-n reads input, line by line, in a loop sending to $_ Equivalent to while () { mycode } -e execute the following quoted string (i.e. do the following on the same line as the perl command) the elipses .. operator behaves like a range, remembering the state from line to line.

Print today's date in ISO format without calling an external command (bash 4)


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