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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"

Alternative for basename using grep to extract file name
Here's a bash version.

Speak the top 6 lines of your twitter timeline every 5 minutes.....
Pump up the chatter, run this script on a regular basis to listen to your twitter timeline. This is a rough first cut using several cli clips I have spotted around. There is no facility to not read those things already read to you. This could also easily be put in a loop for timed onslaught from the chatterverse, though I think it might violate several pointsof the Geneva Convention UPDATE - added a loop, only reads the first 6 twits, and does this every 5 mins.

Synchronize date and time with a server over ssh
Shorter, easier to remember version of cmd#7636 NTP is better, but there are situations where it can't be used. In those cases, you can do this to sync the local time to a server.

Recursive find and replace file extension / suffix (mass rename files)
Find recursively all files in ~/Notes with the extension '.md' and pipe that via xargs to rename command, which will replace every '.md' to '.txt' in this example (existing files will not be overwritten).

Create a tar archive using xz compression
compress directory archive with xz compression, if tar doesn't have the -J option (OSX tar doesn't have -J)

pipe output to notify-send
you can put almost any command. $notify-send -t 0 "MOTD" "$(sed -n '/#^4/,/#$4/{/#^4\|#$4/!p}' motd2 | cut -d# -f2)" $notify-send -t 0 "readfile" "$(while read mess; do echo $mess;done < motd2)"

Diff two directories by finding and comparing the md5 checksums of their contents.
Compute the md5 checksums for the contents of two mirrored directories, then sort and diff the results. If everything matches, nothing is returned. Otherwise, any checksums which do not match, or which exist in one tree but not the other, are returned. As you might imagine, the output is useful only if no errors are found, because only the checksums, not filenames, are returned. I hope to address this, or that someone else will!

validate the syntax of a perl-compatible regular expression
Place the regular expression you want to validate between the forward slashes in the eval block.

sort ugly text
Often, when sorting you want the sort to ignore extraneous characters. The b, d, and f tell sort to ignore leading blanks, use 'dictionary order' (ignore punctuation), and ignore (fold) case. Add a "u" if you only want one copy of duplicate lines. This is a great command to use within vim to sort lines of text, using !}sort -bdf


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