From: Michael Kerrisk <mtk.manpages@xxxxxxxxx> Date: Sat, 16 May 2020 09:45:11 +0200 Subject: [PATCH] ipcs.1: ipcs no longer needs read permission on IPC resources With changes starting around util-linux commit 058e81540fbb0d2b78 that switched from using IPC_STAT to parsing /proc/sysvipc/*, ipcs now shows all IPC objects rather than just the objects for which the user has read permission. Update the page to reflect this fact, and also add a NOTES section describing the historical and fallback behavior where /proc is not available. Signed-off-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx> --- sys-utils/ipcs.1 | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/sys-utils/ipcs.1 b/sys-utils/ipcs.1 index 93c35e323..4b3baaaa5 100644 --- a/sys-utils/ipcs.1 +++ b/sys-utils/ipcs.1 @@ -8,8 +8,7 @@ ipcs \- show information on IPC facilities [options] .SH DESCRIPTION .B ipcs -shows information on the inter-process communication facilities -for which the calling process has read access. +shows information on inter-process communication facilities. By default it shows information about all three resources: shared memory segments, message queues, and semaphore arrays. .SH OPTIONS @@ -76,6 +75,25 @@ Print sizes in bytes. .TP .B \-\-human Print sizes in human-readable format. +.SH NOTES +The current implementation of +.B ipcs +obtains information about available IPC resources by parsing the files in +.IR /proc/sysvipc . +Before util-linux version v2.23, an alternate mechanism was used: the +.BR IPC_STAT +command of +.BR msgctl (2), +.BR semctl (2), +and +.BR shmctl (2). +This mechanism is also used in later util-linux versions in the case where +.I /proc +is unavailable. +A limitation of the +.B IPC_STAT +mechanism is that it can only be used to retrieve information about +IPC resources for which the user has read permission. .SH SEE ALSO .BR ipcmk (1), .BR ipcrm (1), -- 2.26.2 -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
