NAME¶
explain_fdopen - explain
fdopen(3) errors
SYNOPSIS¶
#include <libexplain/fdopen.h>
const char *explain_fdopen(int fildes, const char *flags);
const char *explain_errno_fdopen(int errnum, int fildes, const char *flags);
void explain_message_fdopen(char *message, int message_size, int fildes, const
char *flags);
void explain_message_errno_fdopen(char *message, int message_size, int errnum,
int fildes, const char *flags);
DESCRIPTION¶
These functions may be used to obtain explanations for errors returned by the
fdopen(3) system call.
explain_fdopen¶
const char *explain_fdopen(int fildes, const char *flags);
The
explain_fdopen function is used to obtain an explanation of an error
returned by the
fdopen(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.
This function is intended to be used in a fashion similar to the following
example:
FILE *fp = fdopen(fildes, flags);
if (!fp)
{
fprintf(stderr, "%s\n", explain_fdopen(fildes, flags));
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the
explain_fdopen_or_die(3) function.
- fildes
- The original fildes, exactly as passed to the
fdopen(3) system call.
- flags
- The original flags, exactly as passed to the
fdopen(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.
explain_errno_fdopen¶
const char *explain_errno_fdopen(int errnum, int fildes, const char *flags);
The
explain_errno_fdopen function is used to obtain an explanation of an
error returned by the
fdopen(3) 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:
FILE *fp = fdopen(fildes, flags);
if (!fp)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_fdopen(err, fildes, flags));
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the
explain_fdopen_or_die(3) function.
- 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.
- fildes
- The original fildes, exactly as passed to the
fdopen(3) system call.
- flags
- The original flags, exactly as passed to the
fdopen(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.
explain_message_fdopen¶
void explain_message_fdopen(char *message, int message_size, int fildes, const
char *flags);
The
explain_message_fdopen function may be used to obtain an explanation
of an error returned by the
fdopen(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.
This function is intended to be used in a fashion similar to the following
example:
FILE *fp = fdopen(fildes, flags);
if (!fp)
{
char message[3000];
explain_message_fdopen(message, sizeof(message), fildes, flags);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the
explain_fdopen_or_die(3) function.
- 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.
- fildes
- The original fildes, exactly as passed to the
fdopen(3) system call.
- flags
- The original flags, exactly as passed to the
fdopen(3) system call.
explain_message_errno_fdopen¶
void explain_message_errno_fdopen(char *message, int message_size, int errnum,
int fildes, const char *flags);
The
explain_message_errno_fdopen function may be used to obtain an
explanation of an error returned by the
fdopen(3) 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:
FILE *fp = fdopen(fildes, flags);
if (!fp)
{
int err = errno;
char message[3000];
explain_message_errno_fdopen(message, sizeof(message),
err, fildes, flags);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the
explain_fdopen_or_die(3) function.
- 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.
- fildes
- The original fildes, exactly as passed to the
fdopen(3) system call.
- flags
- The original flags, exactly as passed to the
fdopen(3) system call.
SEE ALSO¶
- fdopen(3)
- stream open functions
- explain_fdopen_or_die(3)
- stream open functions and report errors
COPYRIGHT¶
libexplain version 0.52
Copyright (C) 2008 Peter Miller