 | | In this chapter, we examined the user ID and the group ID. The methods for “converting” these numbers to their text-based counterparts in the password and group files are used regularly by systems programs ranging from the ls command to the electronic mail system to the printer system. The methods for exchanging one user ID or group ID for another are frequently used by programs that must allow users to perform a privileged task. The last section of this chapter described many of the pitfalls the programmer may encounter when implementing these methods. Remember, almost everything the UNIX system does is tied, at some level, to the user ID and/or group ID; it is important to handle these quantities properly. | |
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