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 1.4
       Copyright (C) 2008 Peter Miller

AUTHOR

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

                                                                                 explain_fopen(3)