Provided by: libexplain-dev_1.4.D001-12_amd64 bug

NAME

       explain_vfprintf - explain vfprintf(3) errors

SYNOPSIS

       #include <libexplain/vfprintf.h>
       const char *explain_vfprintf(FILE *fp, const char *format, va_list ap);
       const char *explain_errno_vfprintf(int errnum, FILE *fp, const char *format, va_list ap);
       void explain_message_vfprintf(char *message, int message_size, FILE *fp, const char
       *format, va_list ap);
       void explain_message_errno_vfprintf(char *message, int message_size, int errnum, FILE *fp,
       const char *format, va_list ap);

DESCRIPTION

       These  functions may be used to obtain explanations for errors returned by the vfprintf(3)
       system call.

   explain_vfprintf
       const char *explain_vfprintf(FILE *fp, const char *format, va_list ap);

       The explain_vfprintf function is used to obtain an explanation of an error returned by the
       vfprintf(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.

       fp      The original fp, exactly as passed to the vfprintf(3) system call.

       format  The original format, exactly as passed to the vfprintf(3) system call.

       ap      The original ap, exactly as passed to the vfprintf(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.

       Example:  This  function  is  intended  to  be  used in a fashion similar to the following
       example:
              errno = EINVAL; if (vfprintf(fp, format, ap) < 0)
              {
                  fprintf(stderr, "%s\n", explain_vfprintf(fp, format, ap));
                  exit(EXIT_FAILURE);
              }

       The above  code  example  is  available  pre‐packaged  as  the  explain_vfprintf_or_die(3)
       function.

   explain_errno_vfprintf
       const char *explain_errno_vfprintf(int errnum, FILE *fp, const char *format, va_list ap);

       The  explain_errno_vfprintf function is used to obtain an explanation of an error returned
       by the vfprintf(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.

       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.

       fp      The original fp, exactly as passed to the vfprintf(3) system call.

       format  The original format, exactly as passed to the vfprintf(3) system call.

       ap      The original ap, exactly as passed to the vfprintf(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.

       Example:  This  function  is  intended  to  be  used in a fashion similar to the following
       example:
              errno = EINVAL; if (vfprintf(fp, format, ap) < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_vfprintf(err, fp, format, ap));
                  exit(EXIT_FAILURE);
              }

       The above  code  example  is  available  pre‐packaged  as  the  explain_vfprintf_or_die(3)
       function.

   explain_message_vfprintf
       void explain_message_vfprintf(char *message, int message_size, FILE *fp, const char
       *format, va_list ap);

       The explain_message_vfprintf function is  used  to  obtain  an  explanation  of  an  error
       returned  by the vfprintf(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.

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

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

       fp      The original fp, exactly as passed to the vfprintf(3) system call.

       format  The original format, exactly as passed to the vfprintf(3) system call.

       ap      The original ap, exactly as passed to the vfprintf(3) system call.

       Example: This function is intended to be used  in  a  fashion  similar  to  the  following
       example:
              errno = EINVAL; if (vfprintf(fp, format, ap) < 0)
              {
                  char message[3000];
                  explain_message_vfprintf(message, sizeof(message), fp, format, ap);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The  above  code  example  is  available  pre‐packaged  as  the explain_vfprintf_or_die(3)
       function.

   explain_message_errno_vfprintf
       void explain_message_errno_vfprintf(char *message, int message_size, int errnum, FILE *fp,
       const char *format, va_list ap);

       The  explain_message_errno_vfprintf  function is used to obtain an explanation of an error
       returned by the vfprintf(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.

       message The location in which to store the returned message. If a suitable message  return
               buffer is 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.

       fp      The original fp, exactly as passed to the vfprintf(3) system call.

       format  The original format, exactly as passed to the vfprintf(3) system call.

       ap      The original ap, exactly as passed to the vfprintf(3) system call.

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

       The  above  code  example  is  available  pre‐packaged  as  the explain_vfprintf_or_die(3)
       function.

SEE ALSO

       vfprintf(3)
               formatted output conversion

       explain_vfprintf_or_die(3)
               formatted output conversion and report errors

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2010 Peter Miller

                                                                              explain_vfprintf(3)