1explain_shmctl(3) Library Functions Manual explain_shmctl(3)
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6 explain_shmctl - explain shmctl(2) errors
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9 #include <libexplain/shmctl.h>
10 const char *explain_shmctl(int shmid, int command, struct shmid_ds
11 *data);
12 const char *explain_errno_shmctl(int errnum, int shmid, int command,
13 struct shmid_ds *data);
14 void explain_message_shmctl(char *message, int message_size, int shmid,
15 int command, struct shmid_ds *data);
16 void explain_message_errno_shmctl(char *message, int message_size, int
17 errnum, int shmid, int command, struct shmid_ds *data);
18
20 These functions may be used to obtain explanations for errors returned
21 by the shmctl(2) system call.
22 explain_shmctl
24 const char *explain_shmctl(int shmid, int command, struct shmid_ds
25 *data);
26 The explain_shmctl function is used to obtain an explanation of an
28 error returned by the shmctl(2) system call. The least the message will
29 contain is the value of strerror(errno), but usually it will do much
30 better, and indicate the underlying cause in more detail.
31 The errno global variable will be used to obtain the error value to be
33 decoded.
34 shmid The original shmid, exactly as passed to the shmctl(2) system
36 call.
37 command The original command, exactly as passed to the shmctl(2) system
39 call.
40 data The original data, exactly as passed to the shmctl(2) system
42 call.
43 Returns:
45 The message explaining the error. This message buffer is shared
46 by all libexplain functions which do not supply a buffer in
47 their argument list. This will be overwritten by the next call
48 to any libexplain function which shares this buffer, including
49 other threads.
50 Note: This function is not thread safe, because it shares a return buf‐
52 fer across all threads, and many other functions in this library.
53 Example: This function is intended to be used in a fashion similar to
55 the following example:
56 if (shmctl(shmid, command, data) < 0)
57 {
58 fprintf(stderr, "%s\n", explain_shmctl(shmid, command,
59 data));
60 exit(EXIT_FAILURE);
61 }
62 The above code example is available pre-packaged as the explain_shm‐
64 ctl_or_die(3) function.
65 explain_errno_shmctl
67 const char *explain_errno_shmctl(int errnum, int shmid, int command,
68 struct shmid_ds *data);
69 The explain_errno_shmctl function is used to obtain an explanation of
71 an error returned by the shmctl(2) system call. The least the message
72 will contain is the value of strerror(errno), but usually it will do
73 much better, and indicate the underlying cause in more detail.
74 errnum The error value to be decoded, usually obtained from the errno
76 global variable just before this function is called. This is
77 necessary if you need to call any code between the system call
78 to be explained and this function, because many libc functions
79 will alter the value of errno.
80 shmid The original shmid, exactly as passed to the shmctl(2) system
82 call.
83 command The original command, exactly as passed to the shmctl(2) system
85 call.
86 data The original data, exactly as passed to the shmctl(2) system
88 call.
89 Returns:
91 The message explaining the error. This message buffer is shared
92 by all libexplain functions which do not supply a buffer in
93 their argument list. This will be overwritten by the next call
94 to any libexplain function which shares this buffer, including
95 other threads.
96 Note: This function is not thread safe, because it shares a return buf‐
98 fer across all threads, and many other functions in this library.
99 Example: This function is intended to be used in a fashion similar to
101 the following example:
102 if (shmctl(shmid, command, data) < 0)
103 {
104 int err = errno;
105 fprintf(stderr, "%s\n", explain_errno_shmctl(err, shmid,
106 command, data));
107 exit(EXIT_FAILURE);
108 }
109 The above code example is available pre-packaged as the explain_shm‐
111 ctl_or_die(3) function.
112 explain_message_shmctl
114 void explain_message_shmctl(char *message, int message_size, int shmid,
115 int command, struct shmid_ds *data);
116 The explain_message_shmctl function is used to obtain an explanation of
118 an error returned by the shmctl(2) system call. The least the message
119 will contain is the value of strerror(errno), but usually it will do
120 much better, and indicate the underlying cause in more detail.
121 The errno global variable will be used to obtain the error value to be
123 decoded.
124 message The location in which to store the returned message. If a suit‐
126 able message return buffer is supplied, this function is thread
127 safe.
128 message_size
130 The size in bytes of the location in which to store the
131 returned message.
132 shmid The original shmid, exactly as passed to the shmctl(2) system
134 call.
135 command The original command, exactly as passed to the shmctl(2) system
137 call.
138 data The original data, exactly as passed to the shmctl(2) system
140 call.
141 Example: This function is intended to be used in a fashion similar to
143 the following example:
144 if (shmctl(shmid, command, data) < 0)
145 {
146 char message[3000];
147 explain_message_shmctl(message, sizeof(message), shmid, com‐
148 mand, data);
149 fprintf(stderr, "%s\n", message);
150 exit(EXIT_FAILURE);
151 }
152 The above code example is available pre-packaged as the explain_shm‐
154 ctl_or_die(3) function.
155 explain_message_errno_shmctl
157 void explain_message_errno_shmctl(char *message, int message_size, int
158 errnum, int shmid, int command, struct shmid_ds *data);
159 The explain_message_errno_shmctl function is used to obtain an explana‐
161 tion of an error returned by the shmctl(2) system call. The least the
162 message will contain is the value of strerror(errno), but usually it
163 will do much better, and indicate the underlying cause in more detail.
164 message The location in which to store the returned message. If a suit‐
166 able message return buffer is supplied, this function is thread
167 safe.
168 message_size
170 The size in bytes of the location in which to store the
171 returned message.
172 errnum The error value to be decoded, usually obtained from the errno
174 global variable just before this function is called. This is
175 necessary if you need to call any code between the system call
176 to be explained and this function, because many libc functions
177 will alter the value of errno.
178 shmid The original shmid, exactly as passed to the shmctl(2) system
180 call.
181 command The original command, exactly as passed to the shmctl(2) system
183 call.
184 data The original data, exactly as passed to the shmctl(2) system
186 call.
187 Example: This function is intended to be used in a fashion similar to
189 the following example:
190 if (shmctl(shmid, command, data) < 0)
191 {
192 int err = errno;
193 char message[3000];
194 explain_message_errno_shmctl(message, sizeof(message), err,
195 shmid, command, data);
196 fprintf(stderr, "%s\n", message);
197 exit(EXIT_FAILURE);
198 }
199 The above code example is available pre-packaged as the explain_shm‐
201 ctl_or_die(3) function.
202
204 shmctl(2)
205 shared memory control
206 explain_shmctl_or_die(3)
208 shared memory control and report errors
209
211 libexplain version 1.4
212 Copyright (C) 2011 Peter Miller
213 explain_shmctl(3)