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NAME

       explain_dirfd - explain dirfd(3) errors

SYNOPSIS

       #include <libexplain/dirfd.h>
       const char *explain_dirfd(DIR *dir);
       const char *explain_errno_dirfd(int errnum, DIR *dir);
       void explain_message_dirfd(char *message, int message_size, DIR *dir);
       void explain_message_errno_dirfd(char *message, int message_size, int
       errnum, DIR *dir);

DESCRIPTION

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

   explain_dirfd
       const char *explain_dirfd(DIR *dir);

       The explain_dirfd function is used to obtain an explanation of an error
       returned by the dirfd(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.

       dir     The  original  dir,  exactly  as  passed to the dirfd(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:
              int result = dirfd(dir);
              if (result < 0)
              {
                  fprintf(stderr, "%s\n", explain_dirfd(dir));
                  exit(EXIT_FAILURE);
              }

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

   explain_errno_dirfd
       const char *explain_errno_dirfd(int errnum, DIR *dir);

       The explain_errno_dirfd function is used to obtain an explanation of an
       error returned by the dirfd(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.

       dir     The original dir, exactly as  passed  to  the  dirfd(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:
              int result = dirfd(dir);
              if (result < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_dirfd(err, dir));
                  exit(EXIT_FAILURE);
              }

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

   explain_message_dirfd
       void explain_message_dirfd(char *message, int message_size, DIR *dir);

       The explain_message_dirfd function is used to obtain an explanation  of
       an  error  returned  by the dirfd(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.

       dir     The  original  dir,  exactly  as  passed to the dirfd(3) system
               call.

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

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

   explain_message_errno_dirfd
       void explain_message_errno_dirfd(char *message, int message_size, int
       errnum, DIR *dir);

       The   explain_message_errno_dirfd   function   is  used  to  obtain  an
       explanation of an error returned by the dirfd(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.

       dir     The original dir, exactly as  passed  to  the  dirfd(3)  system
               call.

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

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

SEE ALSO

       dirfd(3)
               get directory stream file descriptor

       explain_dirfd_or_die(3)
               get directory stream file descriptor and report errors

COPYRIGHT

       libexplain version 0.19
       Copyright (C) 2009 Peter Miller

                                                              explain_dirfd(3)