Sets the user IDs.

    This function is supported on OpenVMS Integrity servers and
    Alpha only.

    Format

      #include  <unistd.h>

      int setreuid  (uid_t ruid, uid_t euid);

1  –  Arguments

 ruid

    The value to which you want the real user ID set.

 euid

    The value to which you want the effective user ID set.

2  –  Description

    The setreuid function sets the real and effective user IDs of
    the current process to the values specified by the ruid and euid
    arguments. If ruid or euid is -1, the corresponding effective or
    real user ID of the current process is left unchanged.

    A process with the IMPERSONATE privilege can set either ID to any
    value. An unprivileged process can set the effective user ID only
    if the euid argument is equal to either the real, effective, or
    saved user ID of the process.

    It is unspecified whether a process without the IMPERSONATE
    privilege is permitted to change the real user ID to match the
    current real, effective, or saved user ID of the process.

    This function requires that long (32-bit) UID/GID support be
    enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
    for more information.

    See also getuid to know how UIC is represented.

3  –  Return Values

    0                  Successful completion.
    -1                 Indicates an error. The function sets errno to
                       one of the following values:

                       o  EINVAL - The value of the ruid or euid
                          argument is invalid or out of range.

                       o  EPERM - The current process does not have
                          the IMPERSONATE privilege, and either an
                          attempt was made to change the effective
                          user ID to a value other than the real user
                          ID or the saved set-user-ID, or an attempt
                          was made to change the real user ID to a
                          value not permitted by the implementation.