On 2025-08-08, Askar Safin [off-list ref] wrote:

 > If there are no messages in the message queue,
 > read(2) will return no data and errno will be set to ENODATA.
 > If the buf argument to read(2) is not large enough to contain the message,
 > read(2) will return no data and errno will be set to EMSGSIZE.

read(2) will return -1 in these cases? If yes, then, please, write this.

Yes (well, the syscall returns -EMSGSIZE). I'll try to add a note
without making the paragraph too wordy...

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/