(libc.info.gz) Setting User ID

Info Catalog

(libc.info.gz) Reading Persona

(libc.info.gz) Users and Groups

(libc.info.gz) Setting Groups

 
 30.6 Setting the User ID
 ========================
 
 This section describes the functions for altering the user ID (real
 and/or effective) of a process.  To use these facilities, you must
 include the header files 'sys/types.h' and 'unistd.h'.
 
  -- Function: int seteuid (uid_t NEWEUID)
      Preliminary: | MT-Safe | AS-Unsafe lock | AC-Unsafe lock | 
      POSIX Safety Concepts.
 
      This function sets the effective user ID of a process to NEWEUID,
      provided that the process is allowed to change its effective user
      ID. A privileged process (effective user ID zero) can change its
      effective user ID to any legal value.  An unprivileged process with
      a file user ID can change its effective user ID to its real user ID
      or to its file user ID. Otherwise, a process may not change its
      effective user ID at all.
 
      The 'seteuid' function returns a value of '0' to indicate
      successful completion, and a value of '-1' to indicate an error.
      The following 'errno' error conditions are defined for this
      function:
 
      'EINVAL'
           The value of the NEWEUID argument is invalid.
 
      'EPERM'
           The process may not change to the specified ID.
 
      Older systems (those without the '_POSIX_SAVED_IDS' feature) do not
      have this function.
 
  -- Function: int setuid (uid_t NEWUID)
      Preliminary: | MT-Safe | AS-Unsafe lock | AC-Unsafe lock | 
      POSIX Safety Concepts.
 
      If the calling process is privileged, this function sets both the
      real and effective user ID of the process to NEWUID.  It also
      deletes the file user ID of the process, if any.  NEWUID may be any
      legal value.  (Once this has been done, there is no way to recover
      the old effective user ID.)
 
      If the process is not privileged, and the system supports the
      '_POSIX_SAVED_IDS' feature, then this function behaves like
      'seteuid'.
 
      The return values and error conditions are the same as for
      'seteuid'.
 
  -- Function: int setreuid (uid_t RUID, uid_t EUID)
      Preliminary: | MT-Safe | AS-Unsafe lock | AC-Unsafe lock | 
      POSIX Safety Concepts.
 
      This function sets the real user ID of the process to RUID and the
      effective user ID to EUID.  If RUID is '-1', it means not to change
      the real user ID; likewise if EUID is '-1', it means not to change
      the effective user ID.
 
      The 'setreuid' function exists for compatibility with 4.3 BSD Unix,
      which does not support file IDs.  You can use this function to swap
      the effective and real user IDs of the process.  (Privileged
      processes are not limited to this particular usage.)  If file IDs
      are supported, you should use that feature instead of this
      function.   Enable/Disable Setuid.
 
      The return value is '0' on success and '-1' on failure.  The
      following 'errno' error conditions are defined for this function:
 
      'EPERM'
           The process does not have the appropriate privileges; you do
           not have permission to change to the specified ID.
 

Info Catalog

(libc.info.gz) Reading Persona

(libc.info.gz) Users and Groups

(libc.info.gz) Setting Groups