NAME¶
explain_read - explain
read(2) errors
SYNOPSIS¶
#include <libexplain/read.h>
const char *explain_read(int fildes, const void *data, long data_size);
const char *explain_errno_read(int errnum, int fildes, const void *data, long
data_size);
void explain_message_read(char *message, int message_size, int fildes, const
void *data, long data_size);
void explain_message_errno_read(char *message, int message_size, int errnum, int
fildes, const void *data, long data_size);
DESCRIPTION¶
These functions may be used to obtain an explanation for
read(2) errors.
explain_read¶
const char *explain_read(int fildes, const void *data, long data_size);
The explain_read function may be used to obtain a human readable explanation of
what went wrong in a
read(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:
ssize_t n = read(fd, data, data_size);
if (n < 0)
{
fprintf(stderr, "%s\n", explain_read(fd, data, data_size));
exit(EXIT_FAILURE);
}
- fildes
- The original fildes, exactly as passed to the
read(2) system call.
- data
- The original data, exactly as passed to the read(2)
system call.
- data_size
- The original data_size, exactly as passed to the
read(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_read¶
const char *explain_errno_read(int errnum, int fildes, const void *data, long
data_size);
The explain_errno_read function may be used to obtain a human readable
explanation of what went wrong in a
read(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:
ssize_t n = read(fd, data, data_size);
if (n < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_read(err, 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 original fildes, exactly as passed to the
read(2) system call.
- data
- The original data, exactly as passed to the read(2)
system call.
- data_size
- The original data_size, exactly as passed to the
read(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_read¶
void explain_message_read(char *message, int message_size, int fildes, const
void *data, long data_size);
The explain_message_read function may be used to obtain a human readable
explanation of what went wrong in a
read(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:
ssize_t n = read(fd, data, data_size);
if (n < 0)
{
char message[3000];
explain_message_read(message, sizeof(message), fd, data, data_size));
fprintf(stderr, "%s\n", 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
read(2) system call.
- data
- The original data, exactly as passed to the read(2)
system call.
- data_size
- The original data_size, exactly as passed to the
read(2) system call.
Note: Given a suitably thread safe buffer, this function is thread safe.
explain_message_errno_read¶
void explain_message_errno_read(char *message, int message_size, int errnum, int
fildes, const void *data, long data_size);
The explain_message_errno_read function may be used to obtain a human readable
explanation of what went wrong in a
read(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:
ssize_t n = read(fd, data, data_size);
if (n < 0)
{
int err = errno;
char message[3000];
explain_message_errno_read(message, sizeof(message), err,
fd, data, data_size);
fprintf(stderr, "%s\n", 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
read(2) system call.
- data
- The original data, exactly as passed to the read(2)
system call.
- data_size
- The original data_size, exactly as passed to the
read(2) system call.
Note: Given a suitably thread safe buffer, this function is thread safe.
COPYRIGHT¶
libexplain version 0.52
Copyright (C) 2008 Peter Miller
AUTHOR¶
Written by Peter Miller <pmiller@opensource.org.au>