The phrase "a decent command" is correct and usable in written English.
It can be used to describe a satisfactory level of skill or proficiency in a particular area, such as language or technical abilities.
Example: "She has a decent command of Spanish, allowing her to hold conversations with native speakers."
Alternatives: "a good grasp" or "a solid understanding".
He also announced that EEA immigrants would have to show a decent command of English.
If you wander around during school vacation (there's a K-12 school in the village) or after classes let out, you'll most likely be followed by smiling kids, with a decent command of English, showing off their school work in notebooks.
The reason you should wait until you have a decent command of the language before you start speaking, or even writing your own sentences (writing other people's sentences out is fine, and helps you with foreign alphabets and spelling) is that if you make mistakes, they often won't be corrected, and therefore bad grammar and pronunciation will be reinforced in your mind, and it will set you back.
Moreover, the opposition fighters, on the defensive, still lack a decent command-and-control structure.
With decent command of his curveball and his changeup, but not of his fastball, Burnett kept the Mariners scoreless until the bottom of the fifth, when they put runners on second and third with no outs.
Most of these children will one day command a decent salary.
But atomized consumers lack the power to command a decent price for this informational property.
In a few months, once demand has settled down, a mint-condition copy Blackstar will still command a decent price".
However, he noted that because he had accepted the minimum salary for a director to get the film made, he was never able to command a decent wage again or the respect of the studio heads.
Of course, there are only a few Scobles or Arringtons out there who can command a decent price for their individual messages.
In short, the type who can make a decent living but would never command the salary Radcliffe did as a teenager.
