HP-UX Reference (11i v1 05/09) - 2 System Calls (vol 5)

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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 calling

process. The super-user’s euid is zero. The following conditions govern setuid’s behavior:

• If the euid is zero,

setuid()

sets the ruid, euid, and suid to uid.

• If the euid is not zero, but 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 running as

super-user, it can change its euid to match its ruid and reset itself to the previous euid value.)

• If euid is not zero, but the argument uid is equal to the euid, and the calling process is a member

of a group that has the

PRIV_SETRUGID

privilege (see privgrp(4)), 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 cal-

ling process. The following conditions govern

setgid()’s behavior:

• If euid is zero, setgid() sets the rgid and egid to gid.

• If euid is not zero, but the argument gid is equal to the rgid or the sgid,

setgid() sets the egid

to gid; the rgid and sgid remain unchanged.

• If euid is not zero, but the argument gid is equal to the egid, and the calling process is a member of

a group that has the

PRIV_SETRUGID

privilege (see privgrp(4)), setgid() sets the rgid to

gid; the egid and sgid remain unchanged.

RETURN VALUE

Upon successful completion,

setuid() and setgid() returned 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)) are recommended

instead.

AUTHOR

setuid() was developed by AT&T, the University of California, Berkeley, and HP.

setgid() was developed by AT&T.