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setuid.2 (2010 09)

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setuid(2) setuid(2)
NAME
setuid(), setgid() - set user and group IDs
SYNOPSIS
#include <unistd.h>
int setuid(uid_t uid);
int setgid(gid_t gid);
DESCRIPTION
setuid() sets the real-user-ID (ruid ), effective-user-ID (euid), and/or saved-user-ID (suid) of the cal-
ling process. If the Security Containment product is installed, these interfaces treat a process observing
CHSUBJIDENT as a privileged process. Otherwise, only processes with an euid of zero are treated as
privileged processes. See privileges (5) for more information on Security Containment and fine-grained
privileges.
The following conditions govern setuid ’s behavior:
• If the process is privileged,
setuid()
sets the ruid, euid, and suid to uid.
• If the process is not privileged and the argument uid is equal to the ruid or the suid ,
setuid()
sets the euid to uid; the ruid and suid remain unchanged. (If a set-user-ID program is not run-
ning as superuser, it can change its euid to match its ruid and reset itself to the previous euid
value.)
• If the process is not privileged, the argument uid is equal to the euid , and the calling process has
the
PRIV_SETRUGID privilege, setuid()
sets the ruid to uid ; the euid and suid remain
unchanged.
setgid() sets the real-group-ID (rgid), effective-group-ID (egid ), and/or saved-group-ID (sgid) of the
calling process. The following conditions govern
setgid()’s behavior:
• If the process is privileged,
setgid() sets the rgid and egid to gid.
• If the process is not privileged and the argument gid is equal to the rgid or the sgid,
setgid()
sets the egid to gid; the rgid and sgid remain unchanged.
• If the process is not privileged, the argument gid is equal to the egid, and the calling process has
the
PRIV_SETRUGID privilege, setgid()
sets the rgid to gid ; the egid and sgid remain
unchanged.
Security Restrictions
Some or all of the actions associated with this system call require the
CHSUBJIDENT privilege.
Processes owned by the superuser have this privilege. Processes owned by other users may have this
privilege, depending on system configuration.
See privileges (5) for more information about privileged access on systems that support fine-grained
privileges.
RETURN VALUE
Upon successful completion, setuid() and setgid() return 0; otherwise, they return −1 and set
errno to indicate the error.
ERRORS
setuid() and setgid() fail and return −1 if any of the following conditions are encountered:
[EPERM] None of the conditions above are met.
[EINVAL] uid (gid) is not a valid user (group) ID.
WARNINGS
It is recommended that the
PRIV_SETRUGID capability be avoided, as it is provided for backward com-
patibility. This feature may be modified or dropped from future HP-UX releases. When changing the
real user ID and real group ID, use of setresuid() and setresgid() (see setresuid (2)) is recom-
mended instead.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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