The phrase "a simple command" is correct and usable in written English.
You can use it when referring to an instruction or directive that is straightforward and easy to understand.
Example: "To turn on the device, just give it a simple command like 'Power on.'"
Alternatives: "an easy instruction" or "a basic directive."
She recommends starting with a simple command, like "Sit".
You can move a window with a simple command.
Vagrant conveniently provides a simple command to run Puppet inside the VM: vagrant provision.
But when she settled into the blocks, she gave herself a simple command.
Several market insiders said that they were bewildered, because in a market where trading losses can pile up in seconds, executives typically have a simple command that can immediately halt trading.
Without leaving their couch they were able to view the image on the television set, and then, with a simple command using the remote control, they transferred the image to a nearby digital picture frame.
The Lucene-based dictionaries can be directly queried through a simple command-line interface.
Remote devices access the IAS by means of a simple command-response protocol (Information Access Protocol--IAP); the LSAP-Sel of IAS itself is well known and equals 0 × 00.
Read/write times were fairly speedy on this one – 25 MB/s write and 30 MB/s read using a simple command-line test in USB 2.0 mode – and this takes into consideration that you need to use Paragon's NTFS add-on to use the drive in Mac/PC mode (you can easily format the drive into any native format but you risk losing the included backup software (which you probably don't want to use anyway)).
Using SPiM, we were able to automate thousands of model simulations using a simple command-line script.
Secondly, the interactive programs were to be used mostly in (shell-script) pipelines, hence they use a simple command-line interface and, where possible, they read from and write to a stream.
