Hi, there are a few POSIX compliance issues with the "renice" command from util-linux. First and more importantly, per POSIX, like for "nice", "-n" is meant to take an "increment"/"adjustment", not an absolute value. As in renice -n 5 "$pid" is meant to increase the nice value by 5. While the traditional, BSD-style: renice 5 "$pid" sets its absolute value to 5. util-linux added "-n" in 2009 for POSIX compliance (see https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/?id=7cfbafda9c484a8cadefc47ee115086e803d9391), but the "-n" is just ignored. Since 2010, the --help message does say that -n/--priority takes an "increment" (https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/?id=296351b0f112c821bffbe8ce7aa35d716251051d) but that's not what happens in practice (it still sets the niceness to the value specified). $ nice -n 1 sh -c 'renice -n 2 "$$"; ps -o nice,comm -p "$$"; exit' 29606 (process ID) old priority 1, new priority 2 NI COMMAND 2 sh Also, a POSIX renice utility is meant to parse the options the usual (getopt(3)) way. In particular, renice -gn 1 -- 123 Is meant to increase the niceness of pgid 123 by 1, but fails in util-linux renice. $ renice -gn 1 -- "$$" renice: invalid priorty '-gn' Try 'renice --help' for more information. -p, -g, -u are meant to specify how *all* operands are to be interpreted, they are not options that take arguments. renice +1 123 renice +1 123 -u me are unspecified by POSIX, so it's fine for util-linux to handle the BSD way, but renice -n 1 -u me -p 123 Is meant to increase the niceness of users "me", "-p" and "123". Also, calling it "--priority" is quite misleading as the niceness is rather the opposite of priority. GNU "nice" uses "--adjustment" as the long-option equivalent of "-n" (note that FreeBSD also calls it "priority" though).. IMO, the best way to handle it would be to do a BSD-style parsing when the first argument matches the [-+]?\d+ RE, and do a POSIX getopt_long parsing otherwise with: Change the (POSIX style) options to: -n/--adjustment <num>: niceness increment -v/--value (deprecated: --priority) <num>: exact niceness value -g/--pgrp (no arg): interpret operands as gids. -u/--user (no arg): interpret operands as user names/ids -p/-pid (no arg): interpret operands as pids. --help/--version... And keep the renice niceness [[-p/--pid] pid ...] [[-g/--pgrp] pgid ...] [[-u/--user] user ...] usage for backward compatibility and BSD compatibility. Note that there's currently a bug in the latest version of the POSIX specification in that it says that positive increments should *decrease* the niceness (http://austingroupbugs.net/view.php?id=1286). See https://unix.stackexchange.com/questions/541673/how-do-i-start-a-shell-the-way-all-the-processes-ran-from-within-it-and-processe/541691#541691 for more details. -- Stephane
