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check open ports without netstat or lsof

python smtp server
This command will start a simple SMTP server listening on port 1025 of localhost. This server simply prints to standard output all email headers and the email body.

list files with last modified at the end

Doing some floating point calculations with rounding (e.g. at the 3rd decimal)

bulk rename files with sed, one-liner
Far from my favorite, but works in sh and with an old sed that doesn't support '-E'

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"

Format partition with ext4 but without a journal
For slow flash memory (cheap thumb drive), ext4 is the fastest stable file system for all use cases with no relevant exception: http://www.linuxplanet.com/linuxplanet/tutorials/7208/1 Since we can usually dispense with the benefits of a journal for this type of storage, this is a way to achieve the least awful I/O-speed. Disabling the journal for an existing ext4 partition can be achieved using $ tune2fs -O ^has_journal /dev/sdXN Note that it is often recommended to format removable flash media with ext2, due to the lack of a journal. ext4 has many advantages over ext2 even without the journal, with much better speed as one of the consequences. So the only usecase for ext2 would be compatibility with very old software.

Retrieve "last modified" timestamp of web resource in UTC seconds
This command line assumes that "${url}" is the URL of the web resource. It can be useful to check the "freshness" of a download URL before a GET request.

Create a local compressed tarball from remote host directory
This improves on #9892 by compressing the directory on the remote machine so that the amount of data transferred over the network is much smaller. The command uses ssh(1) to get to a remote host, uses tar(1) to archive and compress a remote directory, prints the result to STDOUT, which is written to a local file. In other words, we are archiving and compressing a remote directory to our local box.

Install an mpkg from the command line on OSX
Installing most OSX apps is just a matter of dropping it in /Applications, either GUI-wise or with cp -r. However, many packages are distributed in "mpkg" format, and those have to be installed with an installer. If you don't want to go to the trouble of firing up VNC to install an mpkg, you can use the "installer" command. This will install an application from a .mpkg it to /Applications system-wide. To install a program for just one user, replace "-target /" with "-target username".


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