1explain_getgroups(3)       Library Functions Manual       explain_getgroups(3)
2
3
4

NAME

6       explain_getgroups - explain getgroups(2) errors
7

SYNOPSIS

9       #include <libexplain/getgroups.h>
10       const char *explain_getgroups(int data_size, gid_t *data);
11       const char *explain_errno_getgroups(int errnum, int data_size, gid_t
12       *data);
13       void explain_message_getgroups(char *message, int message_size, int
14       data_size, gid_t *data);
15       void explain_message_errno_getgroups(char *message, int message_size,
16       int errnum, int data_size, gid_t *data);
17

DESCRIPTION

19       These functions may be used to obtain explanations for errors  returned
20       by the getgroups(2) system call.
21
22   explain_getgroups
23       const char *explain_getgroups(int data_size, gid_t *data);
24
25       The  explain_getgroups  function is used to obtain an explanation of an
26       error returned by the getgroups(2) system call. The least  the  message
27       will  contain  is  the value of strerror(errno), but usually it will do
28       much better, and indicate the underlying cause in more detail.
29
30       The errno global variable will be used to obtain the error value to  be
31       decoded.
32
33       data_size
34               The  original  data_size, exactly as passed to the getgroups(2)
35               system call.
36
37       data    The original data, exactly as passed to the getgroups(2) system
38               call.
39
40       Returns:
41               The message explaining the error. This message buffer is shared
42               by all libexplain functions which do not  supply  a  buffer  in
43               their argument list.  This will be overwritten by the next call
44               to any libexplain function which shares this buffer,  including
45               other threads.
46
47       Note: This function is not thread safe, because it shares a return buf‐
48       fer across all threads, and many other functions in this library.
49
50       Example: This function is intended to be used in a fashion  similar  to
51       the following example:
52              if (getgroups(data_size, data) < 0)
53              {
54                  fprintf(stderr, "%s\n", explain_getgroups(data_size, data));
55                  exit(EXIT_FAILURE);
56              }
57
58       The  above  code  example is available pre‐packaged as the explain_get‐
59       groups_or_die(3) function.
60
61   explain_errno_getgroups
62       const char *explain_errno_getgroups(int errnum, int data_size, gid_t
63       *data);
64
65       The  explain_errno_getgroups  function is used to obtain an explanation
66       of an error returned by the getgroups(2) system call.   The  least  the
67       message  will  contain  is the value of strerror(errno), but usually it
68       will do much better, and indicate the underlying cause in more detail.
69
70       errnum  The error value to be decoded, usually obtained from the  errno
71               global  variable  just  before this function is called. This is
72               necessary if you need to call any code between the system  call
73               to  be explained and this function, because many libc functions
74               will alter the value of errno.
75
76       data_size
77               The original data_size, exactly as passed to  the  getgroups(2)
78               system call.
79
80       data    The original data, exactly as passed to the getgroups(2) system
81               call.
82
83       Returns:
84               The message explaining the error. This message buffer is shared
85               by  all  libexplain  functions  which do not supply a buffer in
86               their argument list.  This will be overwritten by the next call
87               to  any libexplain function which shares this buffer, including
88               other threads.
89
90       Note: This function is not thread safe, because it shares a return buf‐
91       fer across all threads, and many other functions in this library.
92
93       Example:  This  function is intended to be used in a fashion similar to
94       the following example:
95              if (getgroups(data_size, data) < 0)
96              {
97                  int err = errno;
98                  fprintf(stderr, "%s\n", explain_errno_getgroups(err,
99                  data_size, data));
100                  exit(EXIT_FAILURE);
101              }
102
103       The  above  code  example is available pre‐packaged as the explain_get‐
104       groups_or_die(3) function.
105
106   explain_message_getgroups
107       void explain_message_getgroups(char *message, int message_size, int
108       data_size, gid_t *data);
109
110       The explain_message_getgroups function is used to obtain an explanation
111       of an error returned by the getgroups(2) system call.   The  least  the
112       message  will  contain  is the value of strerror(errno), but usually it
113       will do much better, and indicate the underlying cause in more detail.
114
115       The errno global variable will be used to obtain the error value to  be
116       decoded.
117
118       message The location in which to store the returned message. If a suit‐
119               able message return buffer is supplied, this function is thread
120               safe.
121
122       message_size
123               The  size  in  bytes  of  the  location  in  which to store the
124               returned message.
125
126       data_size
127               The original data_size, exactly as passed to  the  getgroups(2)
128               system call.
129
130       data    The original data, exactly as passed to the getgroups(2) system
131               call.
132
133       Example: This function is intended to be used in a fashion  similar  to
134       the following example:
135              if (getgroups(data_size, data) < 0)
136              {
137                  char message[3000];
138                  explain_message_getgroups(message, sizeof(message),
139                  data_size, data);
140                  fprintf(stderr, "%s\n", message);
141                  exit(EXIT_FAILURE);
142              }
143
144       The above code example is available pre‐packaged  as  the  explain_get‐
145       groups_or_die(3) function.
146
147   explain_message_errno_getgroups
148       void explain_message_errno_getgroups(char *message, int message_size,
149       int errnum, int data_size, gid_t *data);
150
151       The explain_message_errno_getgroups  function  is  used  to  obtain  an
152       explanation  of an error returned by the getgroups(2) system call.  The
153       least the message will contain is the  value  of  strerror(errno),  but
154       usually  it  will  do much better, and indicate the underlying cause in
155       more detail.
156
157       message The location in which to store the returned message. If a suit‐
158               able message return buffer is supplied, this function is thread
159               safe.
160
161       message_size
162               The size in bytes  of  the  location  in  which  to  store  the
163               returned message.
164
165       errnum  The  error value to be decoded, usually obtained from the errno
166               global variable just before this function is  called.  This  is
167               necessary  if you need to call any code between the system call
168               to be explained and this function, because many libc  functions
169               will alter the value of errno.
170
171       data_size
172               The  original  data_size, exactly as passed to the getgroups(2)
173               system call.
174
175       data    The original data, exactly as passed to the getgroups(2) system
176               call.
177
178       Example:  This  function is intended to be used in a fashion similar to
179       the following example:
180              if (getgroups(data_size, data) < 0)
181              {
182                  int err = errno;
183                  char message[3000];
184                  explain_message_errno_getgroups(message, sizeof(message),
185                  err, data_size, data);
186                  fprintf(stderr, "%s\n", message);
187                  exit(EXIT_FAILURE);
188              }
189
190       The  above  code  example is available pre‐packaged as the explain_get‐
191       groups_or_die(3) function.
192

SEE ALSO

194       getgroups(2)
195               get/set list of supplementary group IDs
196
197       explain_getgroups_or_die(3)
198               get/set list of supplementary group IDs and report errors
199
201       libexplain version 0.40
202       Copyright (C) 2009 Peter Miller
203
204
205
206                                                          explain_getgroups(3)
Impressum