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A command line calculator in Perl
Once I wrote a command line calculator program in C, then I found this... and added to it a bit. For ease of use I normally use this in a tiny Perl program (which I call pc for 'Perl Calculator') #!/usr/bin/perl -w die "Usage: $0 MATHS\n" unless(@ARGV);for(@ARGV){s/x/*/g;s/v/sqrt /g;s/\^/**/g}; print eval(join('',@ARGV)),$/; It handles square roots, power, modulus: $ pc 1+2 (1 plus 2) 3 $ pc 3x4 (3 times 4) 12 $ pc 5^6 (5 to the power of 6) 15625 $ pc v 49 ( square root of 49 ) 7 $ pc 12/3 (12 divided by 3) 4 $ pc 19%4 (19 modulus 4) 3 (you can string maths together too) $ pc 10 x 10 x 10 1000 $ pc 10 + 10 + 10 / 2 25 $ pc 7 x v49 49

Delete specific sender in mailq

Reload all sysctl variables without reboot
Use `sysctl -p` without argument will only load /etc/sysctl.conf, but user configs always put in /etc/sysctl.d/*.conf, `sysctl --system` will load all the config files

convert doc to pdf
convert to pdf and many other formats and vise versa to get a list of supported formats, run $ unoconv --show

Read aloud a text file in Ubuntu (and other Unixes with espeak installed

livehttpheaders (firefox addon) replacement
Default output-file is "liveh.txt". This uses only BRE, in case you're using an older version of sed(1) that doesn't have support for ERE added. With a modern sed(1), to reduce false positive matches, you might do something like: liveh(){ tcpdump -lnnAs512 -i ${1-} tcp |sed 's/.*GET /GET /;s/.*Host: /Host: /;s/.*POST /POST /;/GET |Host: |POST /!d;/[\"'"'"]/d;/\.\./d;w '"${2-liveh.txt}"'' >/dev/null ;} Anyway, it's easy to clean up the output file with sed(1) later.

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)
Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

Convert an existing Git repo to a bare repo
If you want to turn a Git repo into the origin that folks can push to, you should make it a bare repository. See: http://stackoverflow.com/questions/2199897/git-convert-normal-to-bare-repository

Check reverse DNS
The +short option should make dig less chatty.


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