The problem happens only when we pipe the output of "tail -f" . I am not sure how one can take the truss of "/tail -f test_file | grep 123" . I did little debugging on the tail code. This function "check_output_alive" introduced by the commit (mentioned earlier in the thread) sents SIGPIPE after doing a select () call in AIX. And that makes it exit immediately. fd_set rfd; FD_ZERO (&rfd); FD_SET (STDOUT_FILENO, &rfd); /* readable event on STDOUT is equivalent to POLLERR, and implies an error condition on output like broken pipe. */ if (select (STDOUT_FILENO + 1, &rfd, NULL, NULL, &delay) == 1) raise (SIGPIPE); } I didn't understand the real reason behind this commit. Thanks Ayappan P From: Bernhard Voelker To: Ayappan P2 , 33946@debbugs.gnu.org Date: 01/03/2019 11:53 PM Subject: bug#33946: tail -f stops abruptly in AIX when piped. Sent by: "Bug-coreutils" On 1/3/19 6:39 PM, Ayappan P2 wrote: >> On 01-Jan-2019, at 10:36 PM, Ayappan P2 wrote: >> Hi, >> >> I am running coreutils 8.30 in AIX machine and it seems like "tail -f" is >> not working as it used to be when the output is piped. >> >> # ./tail -f test_file | grep 123 >> >> (1) root @ aixoss-automation-3: 6.1.0.0: / >> >> It stops immediately and it seems like this commit >> >> https://github.com/coreutils/coreutils/commit/ce0415fda108b7ec35181118fd7a2c9ee70331ee >> >> has introduce this behavior. >> >> I checked in Linux with coreutils 8.30 where it works as like earlier >> versions. >> >> Thanks >> Ayappan P > Anyone has any idea on this issue ? > > Thanks > Ayappan P Thanks for reporting. It's hard (at least for me) to get hold on to an AIX system, so would you post a trace file (from 'truss'), please? Second, is this specific to a certain AIX version? BTW: our tests should have caught this before the release. Do you also get an error during 'make check'? Have a nice day, Berny