Dear Maintainer, POSIX Issue 8 Draft 3 (and all previous) says: 110716 DESCRIPTION 110722 If standard output is associated with a terminal, diagnostic messages shall be deferred until the 110723 pr utility has completed processing. 110829 ASYNCHRONOUS EVENTS 110830 If pr receives an interrupt while writing to a terminal, it shall flush all accumulated error 110831 messages to the screen before terminating. The UNIX® SYSTEM V RELEASE 4 User's Reference Manual says: Diagnostic reports (failed options) are reported at the end of standard output associated with a terminal, rather than interspersed in the output. Why, then $ pr -F <(echo a) /ENOENT <(echo a) 2023-05-17 00:35 /dev/fd/63 Page 1 a pr: /ENOENT: No such file or directory 2023-05-17 00:35 /dev/fd/62 Page 1 a Best,