Hello Jakub, On 2/19/19 10:08 PM, Jakub Wilk wrote: > The isatty(3) man page says the function fails with EINVAL when "fd > refers to a file other than a terminal. POSIX.1 specifies the error > ENOTTY for this case." > > But I couldn't reproduce this bug. For me, it fails with ENOTTY, as > prescribed by POSIX. > > I've tested this on the following systems: > * Debian unstable (Linux 4.19, glibc 2.28) > * CentOS 5.0 (Linux 2.6.16, glibc 2.5) > > The source code for the test program I used is attached. Thanks for the test program and the report. So, I'm the one that added that text to the page originally. I don't remember which kinds of files/devices gave EINVAL back then, and unfortunately, I did not record info about the testing I did. But, in the meantime, things seem to have changed. As things stand, every non-tty that I test on a recent 4.x kernel fails with ENOTTY. Back when I wrote the manual page text 10 years ago, it's less clear. I went away now and tested a 2.6.32 kernel. FIFOs and pipes fail with EINVAL, but plain text files and directories (for example) fail with ENOTTY. I've applied the patch below. Cheers, Michael diff --git a/man3/isatty.3 b/man3/isatty.3 index 60639c617..ffb0ff24c 100644 --- a/man3/isatty.3 +++ b/man3/isatty.3 @@ -52,13 +52,15 @@ is set to indicate the error. .I fd is not a valid file descriptor. .TP -.B EINVAL +.B ENOTTY .I fd refers to a file other than a terminal. -POSIX.1 specifies the error -.BR ENOTTY -.\" FIXME . File a bug for this? -for this case. +On some older kernels, some types of files +.\" e.g., FIFOs and pipes on 2.6.32) +resulted in the error +.B EINVAL +in this case (which is a violation of POSIX, which specifies the error +.BR ENOTTY ). .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
