Hi all, The use of SHM_R SHM_W seems to be common. I found it in this man page date 1995 https://www.freebsd.org/cgi/man.cgi?query=shmget&sektion=2&apropos=0&manpath=FreeBSD+4.2-RELEASE and in linux/shm.h /* permission flag for shmget */ #define SHM_R 0400 /* or S_IRUGO from <linux/stat.h> */ #define SHM_W 0200 /* or S_IWUGO from <linux/stat.h> */ maybe that helps, wh Am 12.04.2019 16:27, schrieb Michael Kerrisk (man-opages): > Nicolai, > > On 4/10/19 12:21 PM, Nicolai Dagestad wrote: >> This patch documents SHM_R and SHM_W. >> It is made in a similar ways to how the mode flags are described in >> open.2. >> >> --- shmget.2 2019-03-06 17:18:27.000000000 +0100 >> +++ shmget.2.new 2019-04-10 12:16:35.855032188 +0200 >> @@ -172,6 +172,17 @@ >> argument of >> .BR open (2). >> Presently, execute permissions are not used by the system. >> + >> +The following symbolic constants are provided for mode. >> +Theese can be >> +.BR OR 'ed >> +together, shifting them right by 3 set the mode for the group, and by >> 6 set the mode for others. >> +.TP >> +.B SHM_R >> +0400 user has read permission >> +.TP >> +.B SHM_W >> +0200 user has write permission >> .PP >> When a new shared memory segment is created, >> its contents are initialized to zero values, and > > These constants exist (and I think they even exist on some other > implementations), but aren't in POSIX, and so I'm not sure it's > sensible to document them. Or, to put things another way, why do > you think they should be documented? > > Thanks, > > Michael
