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NAME

       explain_fopen - explain fopen(3) errors

SYNOPSIS

       #include <libexplain/fopen.h>
       const char *explain_fopen(const char *path, const char *mode);
       const  char  *explain_errno_fopen(int  errnum,  const char *path, const
       char *mode);
       void explain_message_fopen(char *message, int message_size, const  char
       *path, const char *mode);
       void  explain_message_errno_fopen(char  *message, int message_size, int
       errnum, const char *path, const char *mode);

DESCRIPTION

       These functions may be used to obtain explanations for fopen(3) errors.

   explain_fopen
       const char *explain_fopen(const char *path, const char *mode);

       The explain_fopen function is used to obtain an explanation of an error
       returned by the fopen(3) 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:
              FILE *fp = fopen(path, mode);
              if (!fp)
              {
                  const char *message = explain_fopen(path, mode);
                  fprintf(stderr, ’%s0, message);
                  exit(EXIT_FAILURE);
              }

       path    The original path, exactly as passed  to  the  fopen(3)  system
               call.

       mode    The  original  mode,  exactly  as passed to the fopen(3) 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
       buffer across all threads, and many other functions in this library.

   explain_errno_fopen
       const  char  *explain_errno_fopen(int  errnum,  const char *path, const
       char *mode);

       The explain_errno_fopen function is used to obtain an explanation of an
       error returned by the fopen(3) 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.

       This  function  is  intended  to  be  used  in a fashion similar to the
       following example:
              FILE *fp = fopen(path, mode);
              if (!fp)
              {
                  const char *message = explain_errno_fopen(err, path, mode);
                  fprintf(stderr, ’%s0, message);
                  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.

       path    The original path, exactly as passed  to  the  fopen(3)  system
               call.

       mode    The  original  mode,  exactly  as passed to the fopen(3) 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
       buffer across all threads, and many other functions in this library.

   explain_message_fopen
       void  explain_message_fopen(char *message, int message_size, const char
       *path, const char *mode);

       The explain_message_fopen function is used to obtain an explanation  of
       an  error  returned  by the fopen(3) 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:
              FILE *fp = fopen(path, mode);
              if (!fp)
              {
                  char message[3000];
                  explain_message_fopen(message, sizeof(message), path, 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.

       path    The original path, exactly as passed  to  the  fopen(3)  system
               call.

       mode    The  original  mode,  exactly  as passed to the fopen(3) system
               call

   explain_message_errno_fopen
       void explain_message_errno_fopen(char *message, int  message_size,  int
       errnum, const char *path, const char *mode);

       The   explain_message_errno_fopen   function   is  used  to  obtain  an
       explanation of an error returned by  the  fopen(3)  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.

       This  function  is  intended  to  be  used  in a fashion similar to the
       following example:
              FILE *fp = fopen(path, mode);
              if (!fp)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_fopen(message, sizeof(message), err, path,
                      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.

       path    The  original  path,  exactly  as passed to the fopen(3) system
               call.

       mode    The original mode, exactly as passed  to  the  fopen(3)  system
               call.

COPYRIGHT

       libexplain version
       Copyright (C) 2008 Peter Miller

AUTHOR

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

                                                              explain_fopen(3)