Commands using passwd (18)

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Find recursively, from current directory down, files and directories whose names contain single or multiple whitespaces and replace each such occurrence with a single underscore.
Note the g for global in the perl expression; without it, only the first occurrence in the name would be replaced.

Create directory named after current date
Not a discovery but a useful one nontheless. In the above example date format is 'yyyymmdd'. For other possible formats see 'man date'. This command can be also very convenient when aliased to some meaningful name: $ alias mkdd='mkdir $(date +%Y%m%d)'

Find the process you are looking for minus the grepped one
As an alternative to using an additional grep -v grep you can use a simple regular expression in the search pattern (first letter is something out of the single letter list ;-)) to drop the grep command itself.

Copy a file and force owner/group/mode
This is useful when you want to copy a file and also force a user, a group and a mode for that file. Note: if you want to move that file instead of copying it, you can use $install -o user -g group -m 755 /path/to/file /path/to/dir/ && rm -f /path/to/file which will remove the file only if the install command went fine.

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"

Play music from youtube without download
same as above but dumps the stream to a file.

Convert all WMF images to SVG recursively ignoring file extension case
This assumes you have the package installed necessary for converting WMF files. On my Ubuntu box, this is libwmf-bin. I used this command, as libwmf is not on my wife's iMac, so I archived the directories containing the WMF files from OS X, ran them on my Ubuntu box, archived the resulting SVGs, and sent them back to her. Quick, simple and to the point. Searches directories recursively looking for extensions ignoring case. This is much more readable and clean than -exec for find. The while loop also gives further flexibility on complex logic. Also, although there is 'wmf2svg --auto', it expects lowercase extensions, and not uppercase. Because I want to ignore case, I need to use the -o option instead. Works in ZSH and BASH. Haven't tested in other shells.

Display unique values of a column
the column number is '6'

Extract android adb ab backup to tar format (only works for non encrypted backups)

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }


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