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NAME

       explain_access - explain access(2) errors

SYNOPSIS

       #include <libexplain/access.h>
       const char *explain_access(const char *pathname, int mode);
       const  char *explain_errno_access(int errnum, const char *pathname, int
       mode);
       void explain_message_access(char *message, int message_size, const char
       *pathname, int mode);
       void  explain_message_errno_access(char *message, int message_size, int
       errnum, const char *pathname, int mode);

DESCRIPTION

       These functions may  be  used  to  obtain  explanations  for  access(2)
       errors.

   explain_access
       const char *explain_access(const char *pathname, int mode);

       The  explain_access  function  is  used  to obtain an explanation of an
       error returned by the access(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 = access(pathname, mode);
              if (fd < 0)
              {
                  fprintf(stderr, "%s0, explain_access(pathname, mode));
                  exit(EXIT_FAILURE);
              }

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

       mode    The  original  mode,  exactly as passed to the access(2) system
               call.  TP 8n 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_access
       const  char *explain_errno_access(int errnum, const char *pathname, int
       mode);

       The explain_errno_access function is used to obtain an  explanation  of
       an  error returned by the access(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 = access(pathname, mode);
              if (fd < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s0, explain_errno_access(err, pathname,
                      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  access(2)
               system call.

       mode    The  original  mode,  exactly as passed to the access(2) 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_access
       void explain_message_access(char *message, int message_size, const char
       *pathname, int mode);

       The explain_message_access function is used to obtain an explanation of
       an  error returned by the access(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 = access(pathname, mode);
              if (fd < 0)
              {
                  char message[3000];
                  explain_message_access(message, sizeof(message), pathname,
                      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  access(2)
               system call.

       mode    The  original  mode,  exactly as passed to the access(2) system
               call.

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

       The   explain_message_errno_access   function  is  used  to  obtain  an
       explanation of an error returned by the  access(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 = access(pathname, mode);
              if (fd < 0)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_access(message, sizeof(message), err,
                      pathname, 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 access(2)
               system call.

       mode    The original mode, exactly as passed to  the  access(2)  system
               call.

COPYRIGHT

       libexplain version
       Copyright (C) 2008 Peter Miller

AUTHOR

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

                                                             explain_access(3)