Why is ‘ls’ ‘ls?’


You probably type it every day: ls. It’s a Unix command that shows something like this:

{22:51}~/Downloads/BeOS 5.0 Professional ➭ ls
BeOS_5.0_Professional.ccd BeOS_5.0_Professional.img winworldpc.com.txt
BeOS_5.0_Professional.cue BeOS_5.0_Professional.sub

A simple list of files, quickly presented. But this simple command has its roots in 40-year-old technology.

The first “ls”-like command appeared in 1961 on the Massachusetts Institute of Technology’s Compatible Time-Sharing System, one of the first multi-user computing systems. The command, then, was “listf” – list files.

In 1963, listf got a little smarter, allowing users to view files in reverse or find information about a specific file. By 1965 the programmers added the “*” wildcard to show multiple files of similar types.

The 1960s saw an explosion in operating system development with the creation of Multics, the Multiplexed Information and Computing Service that launched in 1965. This operating system, built by Professor Fernando J. Corbató, was one of the first to use modern operating system techniques and, if you’re brave, you can dig through the source code here.

Multics is still beloved by collectors. One found an original Multics front panel and hardware. Upon resurrecting it, he wrote:

The system boots up to idle in just under 2 minutes, which, from what I understand, is blazingly fast.

A few years later and Multics was already obsolete. Bell Labs turned to two programmers to build a new OS, Dennis Ritchie and Ken Thompson. Their OS? UNIX, the forefather to Linux. Ritchie and Thompson launched the first edition on November 3, 1971, and in that OS, almost out of habit, was a command called list which the pair, wanting to save time, abbreviated to ‘ls.’

Now, ‘ls’ is available on nearly every platform and every device. Even your phone has the ‘ls’ command hidden inside it.

If you’re a techie, you probably type ‘ls’ 100 times a day which adds up to about 400,000 individual instances a year. It’s a little program that does so mich and, ultimately, is one of the most important in the world.

Little things mean a lot, don’t they?

The VisibleMagic Team

Need help with a development project, big or small? Need machine learning, blockchain, hardware, or just a web app? VisibleMagic has got your back. Reply to this email and let’s chat.


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