libexplain/getgroups.h File Reference

explain getgroups(2) errors More...

#include <libexplain/gcc_attributes.h>
#include <libexplain/large_file_support.h>
#include <unistd.h>

Go to the source code of this file.

Functions
int	explain_getgroups_or_die (int data_size, gid_t *data)
int	explain_getgroups_on_error (int data_size, gid_t *data) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_getgroups (int data_size, gid_t *data) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_getgroups (int errnum, int data_size, gid_t *data) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_getgroups (char *message, int message_size, int data_size, gid_t *data)
void	explain_message_errno_getgroups (char *message, int message_size, int errnum, int data_size, gid_t *data)

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Detailed Description

explain getgroups(2) errors

These functions may be used to obtain explanations for errors returned by the getgroups(2) system call.

Definition in file getgroups.h.

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Function Documentation

const char* explain_errno_getgroups	(	int	errnum,
		int	data_size,
		gid_t *	data
	)

The explain_errno_getgroups function is used to obtain an explanation of an error returned by the getgroups(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.

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.
data_size	The original data_size, exactly as passed to the getgroups(2) system call.
data	The original data, exactly as passed to the getgroups(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.

Example:

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

 if (getgroups(data_size, data) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_getgroups(err, data_size, data));
     exit(EXIT_FAILURE);
 }

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

const char* explain_getgroups	(	int	data_size,
		gid_t *	data
	)

The explain_getgroups function is used to obtain an explanation of an error returned by the getgroups(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.

Parameters:

data_size	The original data_size, exactly as passed to the getgroups(2) system call.
data	The original data, exactly as passed to the getgroups(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.

Example:

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

 if (getgroups(data_size, data) < 0)
 {
     fprintf(stderr, "%s\n", explain_getgroups(data_size, data));
     exit(EXIT_FAILURE);
 }

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

int explain_getgroups_on_error	(	int	data_size,
		gid_t *	data
	)

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

Parameters:

data_size	The data_size, exactly as to be passed to the getgroups(2) system call.
data	The data, exactly as to be passed to the getgroups(2) system call.

Returns:

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

Example:

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

 if (explain_getgroups_on_error(data_size, data) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

int explain_getgroups_or_die	(	int	data_size,
		gid_t *	data
	)

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

Parameters:

data_size	The data_size, exactly as to be passed to the getgroups(2) system call.
data	The data, exactly as to be passed to the getgroups(2) system call.

Returns:

This function only returns on success, see getgroups(2) for more information. On failure, prints an explanation and exits, it does not return.

Example:

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

 explain_getgroups_or_die(data_size, data);

void explain_message_errno_getgroups	(	char *	message,
		int	message_size,
		int	errnum,
		int	data_size,
		gid_t *	data
	)

The explain_message_errno_getgroups function is used to obtain an explanation of an error returned by the getgroups(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.

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.
data_size	The original data_size, exactly as passed to the getgroups(2) system call.
data	The original data, exactly as passed to the getgroups(2) system call.

Example:

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

 if (getgroups(data_size, data) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_getgroups(message, sizeof(message), err,
         data_size, data);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

void explain_message_getgroups	(	char *	message,
		int	message_size,
		int	data_size,
		gid_t *	data
	)

The explain_message_getgroups function is used to obtain an explanation of an error returned by the getgroups(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.

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.
data_size	The original data_size, exactly as passed to the getgroups(2) system call.
data	The original data, exactly as passed to the getgroups(2) system call.

Example:

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

 if (getgroups(data_size, data) < 0)
 {
     char message[3000];
     explain_message_getgroups(message, sizeof(message), data_size, data);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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