newgrp allows you to spawn a new shell passing it the supplementary group that I'd like to make my effective GID. For starters: $ id -a uid=500(saml) gid=501(saml) groups=501(saml),502(vboxusers),503(jupiter) We can see that this shell is currently configured with my default UID/GID of saml & saml. Touching some files shows that this is the ... More @Wikipedia
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