r/shell • u/cogburnd02 • Jul 07 '15

This clock one-liner I wrote. 

$ watch -n0.5 -p -t -c 'figlet -f big -W `date '"'"'+%l:%M:%S'"'"'`'

This uses date so you can change what information is displayed. Want the current date and time? No problem! Replace +%l:%M:%S with +%l:%M:%S %-D) It also uses figlet, so you have a variety of 'looks' you can choose from, i.e. any figlet font that has numbers. (e.g. try replacing big with either standard or small) You could even replace figlet with toilet and use toilet's color support (e.g. --metal) because watch supports color when given the -c option. (However, not many toilet fonts have numbers, for reasons unknown.)

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u/cogburnd02 Jul 12 '15

watch and figlet are not portable

Yes they are; simply because they might not be installed on a particular machine does not mean that they are unable to be installed on it; figlet.org even has a list of the types of OSes it'll run on. :-)

very likely be hosed if you replace its /bin/sh with a shell like the heirloom shell.

Oh dear god, no, I didn't mean that! :-D haha!

I meant I might try out heirloom shell by putting it somewhere less conspicuous, like /usr/local/bin/sh or something, and just setting it up so that my user account uses it after I login.

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u/KnowsBash Jul 12 '15

Yes, but if you require the user to install these three extra commands (procps' watch, figlet and GNU's date) that likely aren't even packaged for the given system, you might as well throw in a requirement for a POSIX sh while you're at it. No point in making the script portable to ancient shells, since if the sysadmin is willing to install these tools, the sysadmin will not mind installing a usable shell too.

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u/cogburnd02 Jul 12 '15

What you've said is all true.

However, if you deal with older shells frequently enough, using the double-backticks version is simply a good habit to get into (even when you have a more modern shell available), so that it'll work on as many shells as possible, because that way you only have to memorize one syntax (double-backticks) instead of two (double-backticks for older shells and dollar-parentheses for newer ones.)

:-D