| | Unix Incompatibility Notes: UID Setting Functions |
 | | Every running process has at least two UID numbers associated with it, the real UID number, which identifies the user who launched the process, and the effective UID number, which is used to determine what resources the process can access. |
 | | Normally these are the same, but if a program with a set-uid bit set is run, then while the real UID remains that of the user who ran it, the effective UID is that of the user who owns the file. |
 | | I think the new standard is to set the save UID to the new value of the effective UID if either the real uid is changed (to anything) or the effective UID is changed to something other than the real UID. |
| www.unixpapa.com /incnote/setuid.html (1528 words) |