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Rename files in batch

delete multiple files with spaces in filenames (with confirmation)
ls -Q will show the filenames in quotes. xargs -p rm will print all the filenames piped from ls -Q and ask for confirmation before deleting the files. without the -Q switch, if we have spaces in names, then the files won't be deleted.

Append stdout and stderr to a file, and print stderr to the screen [bash]
Useful for cron jobs -- all output will be logged but only errors will cause email to be sent. NB the order of "2>&1" and ">> logfile" is important, it doesn't work if you reverse them (everything goes to the logfile, nothing left for tee).

Check your hard drive for bad blocks (destructive)
WARNING!!! ALL DATA WILL BE LOST!!! This command should ONLY be run on drives that are meant to be wiped. Data destruction will result from running this command with the '-w' switch. You may run this command with the '-n' switch in place of '-w' if you want to retain all data on the drive, however, the test won't be as detailed, since the '-n' switch provides a non-destructive read-write mode only, whereas '-w' switch actually writes patterns while scanning for bad blocks.

Trigger a command each time a file is created in a directory (inotify)
Listens for events in the directory. Each created file is displayed on stdout. Then each fileline is read by the loop and a command is run. This can be used to force permissions in a directory, as an alternative for umask. More details: http://en.positon.org/post/A-solution-to-the-umask-problem%3A-inotify-to-force-permissions

Find last reboot time
Specific to OSX.

Real full backup copy of /etc folder
Yes, rsync(1) supports local directories. And, should anything change, it's trivial to run the command again, and grab only the changes, instead of the full directory.

Find biggest 10 files in current and subdirectories and sort by file size

enumerate with padding
bash2 : for X in $(seq 1 5); do printf "%03g " "$X";done bash3 : for X in {1..5}; do printf "%03g " "$X";done bash4 : echo {001..5}

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"


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