explain_setresgid(3)

NAME
explain_setresgid - explain setresgid(2) errors

SYNOPSIS
#include <libexplain/setresgid.h>

const char *explain_setresgid(gid_t rgid, gid_t egid, gid_t sgid);
const char *explain_errno_setresgid(int errnum, gid_t rgid, gid_t egid, gid_t sgid);
void explain_message_setresgid(char *message, int message_size, gid_t rgid, gid_t egid, gid_t sgid);
void explain_message_errno_setresgid(char *message, int message_size, int errnum, gid_t rgid, gid_t egid, gid_t sgid);

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

  explain_setresgid
const char *explain_setresgid(gid_t rgid, gid_t egid, gid_t sgid);

The explain_setresgid function is used to obtain an explanation of an error returned by the setresgid(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.

rgid
    The original rgid, exactly as passed to the setresgid(2) system call.

egid
    The original egid, exactly as passed to the setresgid(2) system call.

sgid
    The original sgid, exactly as passed to the setresgid(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 (setresgid(rgid, egid, sgid) < 0)
    {
    fprintf(stderr, "%s\n", explain_setresgid(rgid, egid, sgid));
        exit(EXIT_FAILURE);
    }

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

  explain_errno_setresgid
const char *explain_errno_setresgid(int errnum, gid_t rgid, gid_t egid, gid_t sgid);

The explain_errno_setresgid function is used to obtain an explanation of an error returned by the setresgid(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.

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.

rgid
    The original rgid, exactly as passed to the setresgid(2) system call.

egid
    The original egid, exactly as passed to the setresgid(2) system call.

sgid
    The original sgid, exactly as passed to the setresgid(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 (setresgid(rgid, egid, sgid) < 0)
    {
        int err = errno;
    fprintf(stderr, "%s\n", explain_errno_setresgid(err, rgid, egid, sgid));
        exit(EXIT_FAILURE);
    }

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

  explain_message_setresgid
void explain_message_setresgid(char *message, int message_size, gid_t rgid, gid_t egid, gid_t sgid);

The explain_message_setresgid function is used to obtain an explanation of an error returned by the setresgid(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.

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.

rgid
    The original rgid, exactly as passed to the setresgid(2) system call.

egid
    The original egid, exactly as passed to the setresgid(2) system call.

sgid
    The original sgid, exactly as passed to the setresgid(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    if (setresgid(rgid, egid, sgid) < 0)
    {
        char message[3000];
    explain_message_setresgid(message, sizeof(message), rgid, egid, sgid);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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

  explain_message_errno_setresgid
void explain_message_errno_setresgid(char *message, int message_size, int errnum, gid_t rgid, gid_t egid, gid_t sgid);

The explain_message_errno_setresgid function is used to obtain an explanation of an error returned by the setresgid(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.

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.

rgid
    The original rgid, exactly as passed to the setresgid(2) system call.

egid
    The original egid, exactly as passed to the setresgid(2) system call.

sgid
    The original sgid, exactly as passed to the setresgid(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    if (setresgid(rgid, egid, sgid) < 0)
    {
        int err = errno;
        char message[3000];
    explain_message_errno_setresgid(message, sizeof(message), err, rgid, egid, sgid);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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

SEE ALSO

setresgid(2)
    set real, effective and saved group ID

explain_setresgid_or_die(3)
    set real, effective and saved group ID and report errors

COPYRIGHT
libexplain version 1.1
Copyright (C) 2012 Peter Miller