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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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Count occurrences per minute in a log file
The cut should match the relevant timestamp part of the logfile, the uniq will count the number of occurrences during this time interval.

Get list of servers with a specific port open
Change the -p argument for the port number. See "man nmap" for different ways to specify address ranges.

last.fm rss parser
Quick and kludgy rss parser for the recent tracks rss feed from last.fm. Extracts artist and track link.

creeate file named after actual date
Create a file with actual date as filename

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"

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"

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.

Ping all hosts on 192.168.1.0/24

Ping a URL sending output to file and STDOUT
The tee (as in "T" junction) command is very useful for redirecting output to two places.

Display the definition of a shell function
Display the code of a previously defined shell function.


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