NAME

       explain_open - explain open(2) errors

SYNOPSIS

       #include <libexplain/open.h>
       const char *explain_open(const char *pathname, int flags, int mode);
       const char *explain_errno_open(int errnum, const char *pathname, int flags, int mode);
       void  explain_message_open(char  *message,  int  message_size,  const  char *pathname, int
       flags, int mode);
       void explain_message_errno_open(char *message, int message_size, int  errnum,  const  char
       *pathname, int flags, int mode);

DESCRIPTION

       These functions may be used to obtains explanations for open(2) errors.

   explain_open(const char *pathname, int flags, int mode);
       const char *explain_open(const char *pathname, int flags, int mode);

       The  explain_open  function  is  used to obtain an explanation of an error returned by the
       open(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.

       This function is intended to be used in a fashion similar to the following example:
              int fd = open(pathname, flags, mode);
              if (fd < 0)
              {
                  fprintf(stderr, '%s0, explain_open(pathname, flags, mode));
                  exit(EXIT_FAILURE);
              }

       pathname
               The original pathname, exactly as passed to the open(2) system call.

       flags   The original flags, exactly as passed to the open(2) system call.

       mode    The  original  mode,  exactly as passed to the open(2) system call (or zero if the
               original call didn't need a mode argument).

       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 buffer across all
       threads, and many other functions in this library.

   explain_errno_open
       const char *explain_errno_open(int errnum, const char *pathname, int flags, int mode);

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

       This function is intended to be used in a fashion similar to the following example:
              int fd = open(pathname, flags, mode);
              if (fd < 0)
              {
                  int err = errno;
                  fprintf(stderr, '%s0, explain_errno_open(err, pathname,
                      flags, mode));
                  exit(EXIT_FAILURE);
              }

       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.

       pathname
               The original pathname, exactly as passed to the open(2) system call.

       flags   The original flags, exactly as passed to the open(2) system call.

       mode    The original mode, exactly as passed to the open(2) system call (or  zero  if  the
               original call didn't need a mode argument).

       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  buffer  across  all
       threads, and many other functions in this library.

   explain_message_open
       void  explain_message_open(char  *message,  int  message_size,  const  char *pathname, int
       flags, int mode);

       The explain_message_open function is used to obtain an explanation of an error returned by
       the   open(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.

       This function is intended to be used in a fashion similar to the following example:
              int fd = open(pathname, flags, mode);
              if (fd < 0)
              {
                  char message[3000];
                  explain_message_open(message, sizeof(message), pathname, flags,
                      mode);
                  fprintf(stderr, '%s0, message);
                  exit(EXIT_FAILURE);
              }

       message The  location  in  which  to store the returned message.  Because a message return
               buffer has been supplied, this function is thread safe.

       message_size
               The size in bytes of the location in which to store the returned message.

       pathname
               The original pathname, exactly as passed to the open(2) system call.

       flags   The original flags, exactly as passed to the open(2) system call.

       mode    The original mode, exactly as passed to the open(2) system call (or  zero  if  the
               original call didn't need a mode argument).

   explain_message_errno_open
       void  explain_message_errno_open(char  *message,  int message_size, int errnum, const char
       *pathname, int flags, int mode);

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

       This function is intended to be used in a fashion similar to the following exameple:
              int fd = open(pathname, flags, mode);
              if (fd < 0)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_open(message, sizeof(message), err, pathname,
                      flags, mode);
                  fprintf(stderr, '%s0, message);
                  exit(EXIT_FAILURE);
              }

       message The  location  in  which  to store the returned message.  Because a message return
               buffer has been supplied, this function is thread safe.

       message_size
               The size in bytes of the location in which to store the returned 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.

       pathname
               The original pathname, exactly as passed to the open(2) system call.

       flags   The original flags, exactly as passed to the open(2) system call.

       mode    The  original  mode,  exactly as passed to the open(2) system call (or zero if the
               original call didn't need a mode argument).

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2008 Peter Miller

AUTHOR

       Written by Peter Miller <pmiller@opensource.org.au>

                                                                                  explain_open(3)