libexplain/dup.h File Reference

explain dup(2) errors More...

#include <libexplain/gcc_attributes.h>

Go to the source code of this file.

Functions
int	explain_dup_or_die (int fildes)
int	explain_dup_on_error (int fildes) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_dup (int fildes) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_dup (int errnum, int fildes) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_dup (char *message, int message_size, int fildes)
void	explain_message_errno_dup (char *message, int message_size, int errnum, int fildes)

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Detailed Description

explain dup(2) errors

Definition in file dup.h.

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Function Documentation

const char* explain_dup

(

int

fildes

)

The explain_dup function is used to obtain an explanation of an error returned by the dup(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:

 int newfd = dup(fildes);
 if (newfd < 0)
 {
     fprintf(stderr, "%s\n", explain_dup(fildes));
     exit(EXIT_FAILURE);
 }

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

Parameters:

fildes

The original fildes, exactly as passed to the dup(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_dup_on_error

(

int

fildes

)

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

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

 int newfd = explain_dup_on_error(fildes);
 if (newfd < 0)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

fildes

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

Returns:

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

int explain_dup_or_die

(

int

fildes

)

The explain_dup_or_die function is used to call the dup(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_dup(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:

 int newfd = explain_dup_or_die(fildes);

Parameters:

fildes

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

Returns:

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

const char* explain_errno_dup	(	int	errnum,
		int	fildes
	)

The explain_errno_dup function is used to obtain an explanation of an error returned by the dup(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:

 int newfd = dup(fildes);
 if (newfd < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_dup(fildes));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_dup_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 dup(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.

void explain_message_dup	(	char *	message,
		int	message_size,
		int	fildes
	)

The explain_message_dup function is used to obtain an explanation of an error returned by the dup(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:

 int newfd = dup(fildes);
 if (newfd < 0)
 {
     char message[3000];
     explain_message_dup(message, sizeof(message), fildes);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_dup_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 dup(2) system call.

void explain_message_errno_dup	(	char *	message,
		int	message_size,
		int	errnum,
		int	fildes
	)

The explain_message_errno_dup function is used to obtain an explanation of an error returned by the dup(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:

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

The above code example is available pre-packaged as the explain_dup_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 dup(2) system call.