Commands by reaper (2)

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a shell function to print a ruler the width of the terminal window.
A similar version for Bash that doesn't require cut and shortens the function in a few places. And it uses local variables. (similar to a version by eightmillion in a comment on the another version)

cycle through everything sox knows how to read, playing only the first three seconds
I wasted two hours reading the sox documentation and searching on the web for the format of some obscure fscking sound sample, and then finally came up with this. This plays only the first three seconds of your unknown formatted sound file using every one of sox's built-in filetypes. If you don't get an exact match, you may get close. . I could not fit every single type in and keep it under 127 characters, so you will have to replace "..." with the full list obtainable by `$ sox --help` (or try `Show sample output`) . note: /usr/bin/play should be linked to sox on most systems.

diff output of two commands
This only works in bash

Generate Random Passwords
If you want a password length longer than 6, changing the -c6 to read -c8 will give you 8 random characters instead of 6. To end up with a line-feed, use this with echo: # echo `< /dev/urandom tr -dc _A-Z-a-z-0-9 | head -c6` Modern systems need higher strenght, so add some special characters: # < /dev/urandom tr -dc '[email protected]#$%qwertQWERTasdfgASDFGzxcvbZXCVB' | head -c8

Efficient count files in directory (no recursion)
$ time perl -e 'if(opendir D,"."){@a=readdir D;print $#a - 1,"\n"}' 205413 real 0m0.497s user 0m0.220s sys 0m0.268s $ time { ls |wc -l; } 205413 real 0m3.776s user 0m3.340s sys 0m0.424s ********* ** EDIT: turns out this perl liner is mostly masturbation. this is slightly faster: $ find . -maxdepth 1 | wc -l sh-3.2$ time { find . -maxdepth 1|wc -l; } 205414 real 0m0.456s user 0m0.116s sys 0m0.328s ** EDIT: now a slightly faster perl version $ perl -e 'if(opendir D,"."){++$c foreach readdir D}print $c-1,"\n"' sh-3.2$ time perl -e 'if(opendir D,"."){++$c foreach readdir D}print $c-1,"\n"' 205414 real 0m0.415s user 0m0.176s sys 0m0.232s

return external ip
Return IP information about your external ip address with JSON format

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"

Empty Bind9 cache
Occasionally, to force zone updating, cache flush is necessary. The use of this command is better than restart the Bind9 process.

Functions to display, save and restore $IFS
You can display, save and restore the value of $IFS using conventional Bash commands, but these functions, which you can add to your ~/.bashrc file make it really easy. To display $IFS use the function ifs shown above. In the sample output, you can see that it displays the characters and their hexadecimal equivalent. This function saves it in a variable called $saveIFS: $ sifs () { saveIFS=$IFS; } Use this function to restore it $ rifs () { IFS=$saveIFS; } Add this line in your ~/.bashrc file to save a readonly copy of $IFS: $ declare -r roIFS=$IFS Use this function to restore that one to $IFS $ rrifs () { IFS=$roIFS; }

File rotation without rename command
Rotates log files with "gz"-extension in a directory for 7 days and enumerates the number in file name. i.e.: logfile.1.gz > logfile.2.gz I needed this line due to the limitations on AIX Unix systems which do not ship with the rename command.

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