explain_getgrent man page

explain_getgrent — explain getgrent(3) errors

Synopsis

#include <libexplain/getgrent.h>

const char *explain_getgrent(void);
const char *explain_errno_getgrent(int errnum, void);
void explain_message_getgrent(char *message, int message_size, void);
void explain_message_errno_getgrent(char *message, int message_size, int errnum, void);

Description

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

explain_getgrent

const char *explain_getgrent(void);

The explain_getgrent function is used to obtain an explanation of an error returned by the getgrent(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.

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; struct group *result = getgrent();
if (!result && errno != 0)

{

fprintf(stderr, "%s\n", explain_getgrent());

    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_getgrent_or_die(3) function.

explain_errno_getgrent

const char *explain_errno_getgrent(int errnum, void);

The explain_errno_getgrent function is used to obtain an explanation of an error returned by the getgrent(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.

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.
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; struct group *result = getgrent();
if (!result && errno != 0)

{
    int err = errno;

fprintf(stderr, "%s\n", explain_errno_getgrent(err, ));

    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_getgrent_or_die(3) function.

explain_message_getgrent

void explain_message_getgrent(char *message, int message_size, void);

The explain_message_getgrent function is used to obtain an explanation of an error returned by the getgrent(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.

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.

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

errno = 0; struct group *result = getgrent();
if (!result && errno != 0)

{
    char message[3000];

explain_message_getgrent(message, sizeof(message), );

    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_getgrent_or_die(3) function.

explain_message_errno_getgrent

void explain_message_errno_getgrent(char *message, int message_size, int errnum, void);

The explain_message_errno_getgrent function is used to obtain an explanation of an error returned by the getgrent(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.

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.

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

errno = 0; struct group *result = getgrent();
if (!result && errno != 0)

{
    int err = errno;
    char message[3000];

explain_message_errno_getgrent(message, sizeof(message), err, );

    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_getgrent_or_die(3) function.

See Also

getgrent(3)
get group file entry
explain_getgrent_or_die(3)
get group file entry and report errors

Referenced By

explain(3), explain_getgrent_or_die(3).