libexplain/dup2.h File Reference

explain dup2(2) errors More...

#include <libexplain/gcc_attributes.h>

Go to the source code of this file.

Functions
void	explain_dup2_or_die (int oldfd, int newfd)
int	explain_dup2_on_error (int oldfd, int newfd) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_dup2 (int oldfd, int newfd) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_dup2 (int errnum, int oldfd, int newfd) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_dup2 (char *message, int message_size, int oldfd, int newfd)
void	explain_message_errno_dup2 (char *message, int message_size, int errnum, int oldfd, int newfd)

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Detailed Description

explain dup2(2) errors

Definition in file dup2.h.

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Function Documentation

const char* explain_dup2	(	int	oldfd,
		int	newfd
	)

The explain_dup2 function is used to obtain an explanation of an error returned by the dup2(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 (dup2(oldfd, newfd) < 0)
 {
     fprintf(stderr, "%s\n", explain_dup2(oldfd, newfd));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_dup2_or_die function.

Parameters:

oldfd	The original oldfd, exactly as passed to the dup2(2) system call.
newfd	The original newfd, exactly as passed to the dup2(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_dup2_on_error	(	int	oldfd,
		int	newfd
	)

The explain_dup2_on_error function is used to call the dup2(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_dup2(3) function.

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

 if (explain_dup2_on_error(oldfd, newfd) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

oldfd	The oldfd, exactly as to be passed to the dup2(2) system call.
newfd	The newfd, exactly as to be passed to the dup2(2) system call.

Returns:

The value returned by the wrapped dup2(2) system call.

void explain_dup2_or_die	(	int	oldfd,
		int	newfd
	)

The explain_dup2_or_die function is used to call the dup2(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_dup2(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_dup2_or_die(oldfd, newfd);

Parameters:

oldfd	The oldfd, exactly as to be passed to the dup2(2) system call.
newfd	The newfd, exactly as to be passed to the dup2(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_dup2	(	int	errnum,
		int	oldfd,
		int	newfd
	)

The explain_errno_dup2 function is used to obtain an explanation of an error returned by the dup2(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 (dup2(oldfd, newfd) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_dup2(err, oldfd, newfd));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_dup2_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.
oldfd	The original oldfd, exactly as passed to the dup2(2) system call.
newfd	The original newfd, exactly as passed to the dup2(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_dup2	(	char *	message,
		int	message_size,
		int	oldfd,
		int	newfd
	)

The explain_message_dup2 function is used to obtain an explanation of an error returned by the dup2(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 (dup2(oldfd, newfd) < 0)
 {
     char message[3000];
     explain_message_dup2(message, sizeof(message), oldfd, newfd);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_dup2_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.
oldfd	The original oldfd, exactly as passed to the dup2(2) system call.
newfd	The original newfd, exactly as passed to the dup2(2) system call.

void explain_message_errno_dup2	(	char *	message,
		int	message_size,
		int	errnum,
		int	oldfd,
		int	newfd
	)

The explain_message_errno_dup2 function is used to obtain an explanation of an error returned by the dup2(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 (dup2(oldfd, newfd) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_dup2(message, sizeof(message), err, oldfd, newfd);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_dup2_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.
oldfd	The original oldfd, exactly as passed to the dup2(2) system call.
newfd	The original newfd, exactly as passed to the dup2(2) system call.