libexplain/getgrouplist.h File Reference

explain getgrouplist(3) errors More...

#include <libexplain/gcc_attributes.h>
#include <libexplain/large_file_support.h>
#include <sys/types.h>

Go to the source code of this file.

Functions
void	explain_getgrouplist_or_die (const char *user, gid_t group, gid_t *groups, int *ngroups)
int	explain_getgrouplist_on_error (const char *user, gid_t group, gid_t *groups, int *ngroups)
const char *	explain_getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_getgrouplist (int errnum, const char *user, gid_t group, gid_t *groups, int *ngroups) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_getgrouplist (char *message, int message_size, const char *user, gid_t group, gid_t *groups, int *ngroups)
void	explain_message_errno_getgrouplist (char *message, int message_size, int errnum, const char *user, gid_t group, gid_t *groups, int *ngroups)

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Detailed Description

explain getgrouplist(3) errors

These functions may be used to obtain explanations for errors returned by the getgrouplist(3) system call.

Definition in file getgrouplist.h.

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Function Documentation

const char* explain_errno_getgrouplist	(	int	errnum,
		const char *	user,
		gid_t	group,
		gid_t *	groups,
		int *	ngroups
	)

The explain_errno_getgrouplist function is used to obtain an explanation of an error returned by the getgrouplist(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.

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.
user	The original user, exactly as passed to the getgrouplist(3) system call.
group	The original group, exactly as passed to the getgrouplist(3) system call.
groups	The original groups, exactly as passed to the getgrouplist(3) system call.
ngroups	The original ngroups, exactly as passed to the getgrouplist(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.

Example:

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

 errno = 0;
 if (getgrouplist(user, group, groups, ngroups) < 0 && errno != 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_getgrouplist(err, user, group,
         groups, ngroups));
     exit(EXIT_FAILURE);
 }

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

const char* explain_getgrouplist	(	const char *	user,
		gid_t	group,
		gid_t *	groups,
		int *	ngroups
	)

The explain_getgrouplist function is used to obtain an explanation of an error returned by the getgrouplist(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.

Parameters:

user	The original user, exactly as passed to the getgrouplist(3) system call.
group	The original group, exactly as passed to the getgrouplist(3) system call.
groups	The original groups, exactly as passed to the getgrouplist(3) system call.
ngroups	The original ngroups, exactly as passed to the getgrouplist(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.

Example:

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

 errno = 0;
 if (getgrouplist(user, group, groups, ngroups) < 0 && errno != 0)
 {
     explain_output_error_and_die("%s\n", explain_getgrouplist(user, group,
         groups, ngroups));
 }

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

int explain_getgrouplist_on_error	(	const char *	user,
		gid_t	group,
		gid_t *	groups,
		int *	ngroups
	)

The explain_getgrouplist_on_error function is used to call the getgrouplist(3) system call. On failure an explanation will be printed to stderr, obtained from the explain_getgrouplist(3) function.

Parameters:

user	The user, exactly as to be passed to the getgrouplist(3) system call.
group	The group, exactly as to be passed to the getgrouplist(3) system call.
groups	The groups, exactly as to be passed to the getgrouplist(3) system call.
ngroups	The ngroups, exactly as to be passed to the getgrouplist(3) system call.

Returns:

The value returned by the wrapped getgrouplist(3) system call.

Example:

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

 errno = 0;
 if (explain_getgrouplist_on_error(user, group, groups, ngroups) < 0 && errno
     != 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_getgrouplist_or_die	(	const char *	user,
		gid_t	group,
		gid_t *	groups,
		int *	ngroups
	)

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

Parameters:

user	The user, exactly as to be passed to the getgrouplist(3) system call.
group	The group, exactly as to be passed to the getgrouplist(3) system call.
groups	The groups, exactly as to be passed to the getgrouplist(3) system call.
ngroups	The ngroups, exactly as to be passed to the getgrouplist(3) system call.

Returns:

This function only returns on success, see getgrouplist(3) 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_getgrouplist_or_die(user, group, groups, ngroups);

void explain_message_errno_getgrouplist	(	char *	message,
		int	message_size,
		int	errnum,
		const char *	user,
		gid_t	group,
		gid_t *	groups,
		int *	ngroups
	)

The explain_message_errno_getgrouplist function is used to obtain an explanation of an error returned by the getgrouplist(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.

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.
user	The original user, exactly as passed to the getgrouplist(3) system call.
group	The original group, exactly as passed to the getgrouplist(3) system call.
groups	The original groups, exactly as passed to the getgrouplist(3) system call.
ngroups	The original ngroups, exactly as passed to the getgrouplist(3) system call.

Example:

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

 errno = 0;
 if (getgrouplist(user, group, groups, ngroups) < 0 && errno != 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_getgrouplist(message, sizeof(message), err, user,
         group, groups, ngroups);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

void explain_message_getgrouplist	(	char *	message,
		int	message_size,
		const char *	user,
		gid_t	group,
		gid_t *	groups,
		int *	ngroups
	)

The explain_message_getgrouplist function is used to obtain an explanation of an error returned by the getgrouplist(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.

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.
user	The original user, exactly as passed to the getgrouplist(3) system call.
group	The original group, exactly as passed to the getgrouplist(3) system call.
groups	The original groups, exactly as passed to the getgrouplist(3) system call.
ngroups	The original ngroups, exactly as passed to the getgrouplist(3) system call.

Example:

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

 errno = 0;
 if (getgrouplist(user, group, groups, ngroups) < 0 && errno != 0)
 {
     char message[3000];
     explain_message_getgrouplist(message, sizeof(message), user, group,
         groups, ngroups);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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