NAME
explain_fileno - explain fileno(3) errors
SYNOPSIS
#include <libexplain/fileno.h>
const char *explain_fileno(FILE *fp);
const char *explain_errno_fileno(int errnum, FILE *fp);
void explain_message_fileno(char *message, int message_size, FILE *fp);
void explain_message_errno_fileno(char *message, int message_size, int
errnum, FILE *fp);
DESCRIPTION
These functions may be used to obtain explanations for errors returned
by the fileno(3) system call.
explain_fileno
const char *explain_fileno(FILE *fp);
The explain_fileno function is used to obtain an explanation of an
error returned by the fileno(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 fileno(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:
if (fileno(fp) < 0)
{
fprintf(stderr, "%s\n", explain_fileno(fp));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_fileno_or_die(3) function.
explain_errno_fileno
const char *explain_errno_fileno(int errnum, FILE *fp);
The explain_errno_fileno function is used to obtain an explanation of
an error returned by the fileno(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 fileno(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:
if (fileno(fp) < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_fileno(err, fp));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_fileno_or_die(3) function.
explain_message_fileno
void explain_message_fileno(char *message, int message_size, FILE *fp);
The explain_message_fileno function is used to obtain an explanation of
an error returned by the fileno(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 fileno(3) system
call.
Example: This function is intended to be used in a fashion similar to
the following example:
if (fileno(fp) < 0)
{
char message[3000];
explain_message_fileno(message, sizeof(message), fp);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_fileno_or_die(3) function.
explain_message_errno_fileno
void explain_message_errno_fileno(char *message, int message_size, int
errnum, FILE *fp);
The explain_message_errno_fileno function is used to obtain an
explanation of an error returned by the fileno(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 fileno(3) system
call.
Example: This function is intended to be used in a fashion similar to
the following example:
if (fileno(fp) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_fileno(message, sizeof(message), err,
fp);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_fileno_or_die(3) function.
SEE ALSO
fileno(3)
check and reset stream status
explain_fileno_or_die(3)
check and reset stream status and report errors
COPYRIGHT
libexplain version 0.19
Copyright (C) 2009 Peter Miller
explain_fileno(3)