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explain_setreuid(3)	   Library Functions Manual	   explain_setreuid(3)

NAME
       explain_setreuid	- explain setreuid(2) errors

SYNOPSIS
       #include	<libexplain/setreuid.h>
       const char *explain_setreuid(uid_t ruid,	uid_t euid);
       const char *explain_errno_setreuid(int errnum, uid_t ruid, uid_t	euid);
       void explain_message_setreuid(char *message, int	message_size, uid_t
       ruid, uid_t euid);
       void explain_message_errno_setreuid(char	*message, int message_size,
       int errnum, uid_t ruid, uid_t euid);

DESCRIPTION
       These  functions	may be used to obtain explanations for errors returned
       by the setreuid(2) system call.

   explain_setreuid
       const char *explain_setreuid(uid_t ruid,	uid_t euid);

       The explain_setreuid function is	used to	obtain an  explanation	of  an
       error  returned	by  the	setreuid(2) system call. The least the message
       will contain is the value of strerror(errno), but usually  it  will  do
       much better, and	indicate the underlying	cause in more detail.

       The  errno global variable will be used to obtain the error value to be
       decoded.

       ruid    The original ruid, exactly as passed to the setreuid(2)	system
	       call.

       euid    The  original euid, exactly as passed to	the setreuid(2)	system
	       call.

       Returns:
	       The message explaining the error. This message buffer is	shared
	       by  all	libexplain  functions  which do	not supply a buffer in
	       their argument list.  This will be overwritten by the next call
	       to  any libexplain function which shares	this buffer, including
	       other threads.

       Note: This function is not thread safe, because it shares a return buf-
       fer across all threads, and many	other functions	in this	library.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      if (setreuid(ruid, euid) < 0)
	      {
		  fprintf(stderr, "%s\n", explain_setreuid(ruid, euid));
		  exit(EXIT_FAILURE);
	      }

       The above code example is available  pre-packaged  as  the  explain_se-
       treuid_or_die(3)	function.

   explain_errno_setreuid
       const char *explain_errno_setreuid(int errnum, uid_t ruid, uid_t	euid);

       The explain_errno_setreuid function is used to obtain an	explanation of
       an error	returned by the	setreuid(2) system call.  The least  the  mes-
       sage  will contain is the value of strerror(errno), but usually it will
       do much better, and indicate the	underlying cause in more detail.

       errnum  The error value to be decoded, usually obtained from the	 errno
	       global  variable	 just  before this function is called. This is
	       necessary if you	need to	call any code between the system  call
	       to  be explained	and this function, because many	libc functions
	       will alter the value of errno.

       ruid    The original ruid, exactly as passed to the setreuid(2)	system
	       call.

       euid    The  original euid, exactly as passed to	the setreuid(2)	system
	       call.

       Returns:
	       The message explaining the error. This message buffer is	shared
	       by  all	libexplain  functions  which do	not supply a buffer in
	       their argument list.  This will be overwritten by the next call
	       to  any libexplain function which shares	this buffer, including
	       other threads.

       Note: This function is not thread safe, because it shares a return buf-
       fer across all threads, and many	other functions	in this	library.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      if (setreuid(ruid, euid) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_setreuid(err, ruid,
		  euid));
		  exit(EXIT_FAILURE);
	      }

       The  above  code	 example  is available pre-packaged as the explain_se-
       treuid_or_die(3)	function.

   explain_message_setreuid
       void explain_message_setreuid(char *message, int	message_size, uid_t
       ruid, uid_t euid);

       The  explain_message_setreuid function is used to obtain	an explanation
       of an error returned by the setreuid(2) system  call.   The  least  the
       message	will  contain  is the value of strerror(errno),	but usually it
       will do much better, and	indicate the underlying	cause in more detail.

       The errno global	variable will be used to obtain	the error value	to  be
       decoded.

       message The location in which to	store the returned message. If a suit-
	       able message return buffer is supplied, this function is	thread
	       safe.

       message_size
	       The  size  in  bytes  of	the location in	which to store the re-
	       turned message.

       ruid    The original ruid, exactly as passed to the setreuid(2)	system
	       call.

       euid    The  original euid, exactly as passed to	the setreuid(2)	system
	       call.

       Example:	This function is intended to be	used in	a fashion  similar  to
       the following example:
	      if (setreuid(ruid, euid) < 0)
	      {
		  char message[3000];
		  explain_message_setreuid(message, sizeof(message), ruid,
		  euid);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       The above code example is available  pre-packaged  as  the  explain_se-
       treuid_or_die(3)	function.

   explain_message_errno_setreuid
       void explain_message_errno_setreuid(char	*message, int message_size,
       int errnum, uid_t ruid, uid_t euid);

       The explain_message_errno_setreuid function is used to obtain an	expla-
       nation  of an error returned by the setreuid(2) system call.  The least
       the message will	contain	is the value of	strerror(errno),  but  usually
       it  will	 do much better, and indicate the underlying cause in more de-
       tail.

       message The location in which to	store the returned message. If a suit-
	       able message return buffer is supplied, this function is	thread
	       safe.

       message_size
	       The size	in bytes of the	location in which  to  store  the  re-
	       turned message.

       errnum  The  error value	to be decoded, usually obtained	from the errno
	       global variable just before this	function is  called.  This  is
	       necessary  if you need to call any code between the system call
	       to be explained and this	function, because many libc  functions
	       will alter the value of errno.

       ruid    The  original ruid, exactly as passed to	the setreuid(2)	system
	       call.

       euid    The original euid, exactly as passed to the setreuid(2)	system
	       call.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      if (setreuid(ruid, euid) < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_setreuid(message, sizeof(message),
		  err, ruid, euid);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       The  above  code	 example  is available pre-packaged as the explain_se-
       treuid_or_die(3)	function.

SEE ALSO
       setreuid(2)
	       set the real and	effective user ID

       explain_setreuid_or_die(3)
	       set the real and	effective user ID and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2012 Peter	Miller

							   explain_setreuid(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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