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Replicate a directory structure dropping the files

Remove executable bit from all files in the current directory recursively, excluding other directories
Useful if you have copied files from an OS without a permission structure (for example, DOS) and you need to disable all executable files but want to be able to descend into your directories.

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"

Filter the output of a file continously using tail and grep
The OPs solution will work, however on some systems (bsd), grep will not filter the data, unless the --line-buffered option is enabled.

Clean swap area after using a memory hogging application
When you run a memory intensive application (VirtualBox, large java application, etc) swap area is used as soon as memory becomes insufficient. After you close the program, the data in swap is not put back on memory and that decreases the responsiveness. Swapoff disables the swap area and forces system to put swap data be placed in memory. Since running without a swap area might be detrimental, swapon should be used to activate swap again. Both swapoff and swapon require root privileges.

List the binaries installed by a Debian package
GNU grep's perl-compatible regular expression(PCRE).

Do some learning...
compgen -c finds everything in your path.

Show used disk space:

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" }

rsync should continue even if connection lost
Manage partial uploads using append option.


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