The effective gid of this process. If you are on a machine that supports membership in multiple groups simultaneously, gives a space separated list of groups you are in. The first number is the one returned bygetegid(), and the subsequent ones bygetgroups(), one of which may be the same as the first number.
Similarly, a value assigned to$) must also be a space-separated list of numbers. The first number sets the effective gid, and the rest (if any) are passed tosetgroups(). To get the effect of an empty list forsetgroups(), just repeat the new effective gid; that is, to force an effective gid of 5 and an effectively emptysetgroups() list, say $) = "5 5".
You can change both the effective gid and the real gid at the same time by usingPOSIX::setgid() (use only a single numeric argument). Changes to$) require a check to$! to detect any possible errors after an attempted change.
$<,$>,$( and$) can be set only on machines that support the correspondingset[re][ug]id() routine.$( and$) can be swapped only on machines supportingsetregid().
Mnemonic: parentheses are used togroup things. The effective gid is the group that'sright for you, if you're running setgid.
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