libexplain/listen.h File Reference

explain listen(2) errors More...

#include <libexplain/gcc_attributes.h>

Go to the source code of this file.

Functions
void	explain_listen_or_die (int fildes, int backlog)
int	explain_listen_on_error (int fildes, int backlog) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_listen (int fildes, int backlog) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_listen (int errnum, int fildes, int backlog) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_listen (char *message, int message_size, int fildes, int backlog)
void	explain_message_errno_listen (char *message, int message_size, int errnum, int fildes, int backlog)

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Detailed Description

explain listen(2) errors

Definition in file listen.h.

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Function Documentation

const char* explain_errno_listen	(	int	errnum,
		int	fildes,
		int	backlog
	)

The explain_errno_listen function is used to obtain an explanation of an error returned by the listen(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:

 if (listen(fildes, backlog) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_listen(err, fildes, backlog));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_listen_or_die function.

Parameters:

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 listen(2) system call.
backlog	The original backlog, exactly as passed to the listen(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.

const char* explain_listen	(	int	fildes,
		int	backlog
	)

The explain_listen function is used to obtain an explanation of an error returned by the listen(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:

 if (listen(fildes, backlog) < 0)
 {
     fprintf(stderr, "%s\n", explain_listen(fildes, backlog));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_listen_or_die function.

Parameters:

fildes	The original fildes, exactly as passed to the listen(2) system call.
backlog	The original backlog, exactly as passed to the listen(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.

int explain_listen_on_error	(	int	fildes,
		int	backlog
	)

The explain_listen_on_error function is used to call the listen(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_listen(3) function.

This function is intended to be used in a fashion similar to the following example:

 if (explain_listen_on_error(fildes, backlog) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

fildes	The fildes, exactly as to be passed to the listen(2) system call.
backlog	The backlog, exactly as to be passed to the listen(2) system call.

Returns:

The value returned by the wrapped listen(2) system call.

void explain_listen_or_die	(	int	fildes,
		int	backlog
	)

The explain_listen_or_die function is used to call the listen(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_listen(3) function, and then the process terminates by calling exit(EXIT_FAILURE).

This function is intended to be used in a fashion similar to the following example:

 explain_listen_or_die(fildes, backlog);

Parameters:

fildes	The fildes, exactly as to be passed to the listen(2) system call.
backlog	The backlog, exactly as to be passed to the listen(2) system call.

Returns:

This function only returns on success. On failure, prints an explanation and exits, it does not return.

void explain_message_errno_listen	(	char *	message,
		int	message_size,
		int	errnum,
		int	fildes,
		int	backlog
	)

The explain_message_errno_listen function is used to obtain an explanation of an error returned by the listen(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:

 if (listen(fildes, backlog) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_listen(message, sizeof(message), err, fildes,
         backlog);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_listen_or_die function.

Parameters:

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 listen(2) system call.
backlog	The original backlog, exactly as passed to the listen(2) system call.

void explain_message_listen	(	char *	message,
		int	message_size,
		int	fildes,
		int	backlog
	)

The explain_message_listen function is used to obtain an explanation of an error returned by the listen(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.

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:

 if (listen(fildes, backlog) < 0)
 {
     char message[3000];
     explain_message_listen(message, sizeof(message), fildes, backlog);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_listen_or_die function.

Parameters:

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 listen(2) system call.
backlog	The original backlog, exactly as passed to the listen(2) system call.