NAME
explain_write - explain write(2) errors
SYNOPSIS
#include <libexplain/write.h>
const char *explain_write(int fildes, const void *data, long
data_size);
const char *explain_errno_write(int errnum, int fildes, const void
*data, long data_size);
void explain_message_write(char *message, int message_size, int fildes,
const void *data, long data_size);
void explain_message_errno_write(char *message, int message_size, int
errnum, int fildes, const void *data, long data_size);
DESCRIPTION
These functions may be used to obtain explanations for write(2) errors
.
explain_write
const char *explain_write(int fildes, const void *data, long
data_size);
The explain_write function may be used to obtain a human readable
explanation of what went wrong in a write(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 error number will be picked up from the errno global variable.
This function is intended to be used in a fashion similar to the
following example:
sszie_t n = write(fd, data, data_size);
if (n < 0)
{
fprintf(stderr, ’%s0, explain_read(fd, data, data_size));
exit(EXIT_FAILURE);
}
fildes The original fildes, exactly as passed to the write(2) system
call.
data The original data, exactly as passed to the write(2) system
call.
data_size
The original data_size, exactly as passed to the write(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_errno_write
const char *explain_errno_write(int errnum, int fildes, const void
*data, long data_size);
The explain_errno_write function may be used to obtain a human readable
explanation of what went wrong in a write(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:
sszie_t n = write(fd, data, data_size);
if (n < 0)
{
int err = errno;
fprintf(stderr, ’%s0, explain_errno_read(errnum, fd, data,
data_size));
exit(EXIT_FAILURE);
}
errnum The error value to be decoded, usually obtain 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.
fildes The orginal fildes, exactly as passed to the write(2) system
call.
data The original data, exactly as passed to the write(2) system
call.
data_size
The original data_size, exactly as passed to the write(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_write
void explain_message_write(char *message, int message_size, int fildes,
const void *data, long data_size);
The explain_message_write function may be used to obtain a human
readable explanation of what went wrong in a write(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 error number will be picked up from the errno global variable.
This function is intended to be used in a fashion similar to the
following example:
sszie_t n = write(fd, data, data_size);
if (n < 0)
{
char message[3000];
explain_message_read(message, sizeof(message), fd, data,
data_size));
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.
fildes The original fildes, exactly as passed to the write(2) system
call.
data The original data, exactly as passed to the write(2) system
call.
data_size
The original data_size, exactly as passed to the write(2)
system call.
Note: Given a suitably thread safe buffer, this function is thread
safe.
explain_message_errno_write
void explain_message_errno_write(char * message, int message_size, int
errnum, int fildes, const void *data, long data_size);
The explain_message_errno_write function may be used to obtain a human
readable explanation of what went wrong in a write(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:
sszie_t n = write(fd, data, data_size);
if (n < 0)
{
int err = errno;
char message[3000];
explain_message_errno_read(message, sizeof(message), errno,
fd, data, data_size));
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 obtain 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.
fildes The original fildes, exactly as passed to the write(2) system
call.
data The original data, exactly as passed to the write(2) system
call.
data_size
The original data_size, exactly as passed to the write(2)
system call.
Note: Given a suitably thread safe buffer, this function is thread
safe.
COPYRIGHT
libexplain version
Copyright (C) 2008 Peter Miller
AUTHOR
Written by Peter Miller <pmiller@opensource.org.au>
explain_write(3)