setfsgid - set group identity used for file system checks
int setfsgid(uid_t fsgid))
setfsgid sets the group ID that the Linux kernel uses to
check for all accesses to the file system. Normally, the
value of fsgid will shadow the value of the effective group
ID. In fact, whenever the effective group ID is changed,
fsgid will also be changed to new value of effective group
An explicit call to setfsgid is usually only used by pro-
grams such as the Linux NFS server that need to change what
group ID is used for file access without a corresponding
change in the real and effective group IDs. A change in the
normal group IDs for a program such as the NFS server is a
security hole that can expose it to unwanted signals from
other group IDs.
setfsgid will only succeed if the caller is the superuser or
if fsgid matches either the real group ID, effective group
ID, saved group ID, or the current value of fsgid.
On success, the previous value of fsgid is returned. On
error, the current value of fsgid is returned.
setfsgid is Linux specific and should not be used in pro-
grams intended to be portable.
No error messages of any kind are returned to the caller. At
the very least, EPERM should be returned when the call