Commands by eitland (1)

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Write comments to your history.
A null operation with the name 'comment', allowing comments to be written to HISTFILE. Prepending '#' to a command will *not* write the command to the history file, although it will be available for the current session, thus '#' is not useful for keeping track of comments past the current session.

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"

list block devices
Shows all block devices in a tree with descruptions of what they are.

Block all IP addresses and domains that have attempted brute force SSH login to computer
I use iptables. To rate limit connections. Very easy and no ban lists to manage.

Replace underscores with spaces in filenames and dirnames, recursively into subdirs.
Everyone wants to take spaces out of filenames. Forget that. I want to put them back in. We've got tools and filesystems that support spaces, they look better, so I'm going to use them. Because of how find works I find I need to run this multiple times, if it's renaming subdirs. But it can be re-run without issues. I got this version of the command from a comment in this underscore-generating command. http://www.commandlinefu.com/commands/view/760/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. All I did was change the regex.

count the number of specific characters in a file or text stream
In this example, the command will recursively find files (-type f) under /some/path, where the path ends in .mp3, case insensitive (-iregex). It will then output a single line of output (-print0), with results terminated by a the null character (octal 000). Suitable for piping to xargs -0. This type of output avoids issues with garbage in paths, like unclosed quotes. The tr command then strips away everything but the null chars, finally piping to wc -c, to get a character count. I have found this very useful, to verify one is getting the right number of before you actually process the results through xargs or similar. Yes, one can issue the find without the -print0 and use wc -l, however if you want to be 1000% sure your find command is giving you the expected number of results, this is a simple way to check. The approach can be made in to a function and then included in .bashrc or similar. e.g. $ count_chars() { tr -d -c "$1" | wc -c; } In this form it provides a versatile character counter of text streams :)

Rename files in batch

list files recursively by size

intercept stdout/stderr of another process
similar to the previous command, but with more friendly output (tested on linux)

Email someone if a web page has been updated.
A cronjob command line to email someone when a webpages homepage is updated.


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