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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.

Download SSL/TLS pem format cert from https web host

When feeling down, this command helps
$ sudo apt-get install sl $ man sl

Limit bandwidth usage by apt-get
Limits the usage of bandwidth by apt-get, in the example the command will use 30Kb/s ;) It should work for most apt-get actions (install, update, upgrade, dist-upgrade, etc.)

Watch active calls on an Asterisk PBX
Only the number of calls nothing else.

Print without executing the last command that starts with...
It happens that sometime you remember that you used a special command short time before and you want to check the command again. WIth this command you can just put the beginning of a command and then bash will look for you and it will print back safely withou executing

Find and copy scattered mp3 files into one directory
No problem with word splitting. That should works on many Unix likes.

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"

Check SSL expiry from commandline

Extract a bash function
I often need to extract a function from a bash script and this command will do it.


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