1explain_getpgid(3) Library Functions Manual explain_getpgid(3)
2
6 explain_getpgid - explain getpgid(2) errors
7
9 #include <libexplain/getpgid.h>
10 const char *explain_getpgid(pid_t pid);
11 const char *explain_errno_getpgid(int errnum, pid_t pid);
12 void explain_message_getpgid(char *message, int message_size, pid_t
13 pid);
14 void explain_message_errno_getpgid(char *message, int message_size, int
15 errnum, pid_t pid);
16
18 These functions may be used to obtain explanations for errors returned
19 by the getpgid(2) system call.
20 explain_getpgid
22 const char *explain_getpgid(pid_t pid);
23 The explain_getpgid function is used to obtain an explanation of an
25 error returned by the getpgid(2) system call. The least the message
26 will contain is the value of strerror(errno), but usually it will do
27 much better, and indicate the underlying cause in more detail.
28 The errno global variable will be used to obtain the error value to be
30 decoded.
31 pid The original pid, exactly as passed to the getpgid(2) system
33 call.
34 Returns:
36 The message explaining the error. This message buffer is shared
37 by all libexplain functions which do not supply a buffer in
38 their argument list. This will be overwritten by the next call
39 to any libexplain function which shares this buffer, including
40 other threads.
41 Note: This function is not thread safe, because it shares a return buf‐
43 fer across all threads, and many other functions in this library.
44 Example: This function is intended to be used in a fashion similar to
46 the following example:
47 pid_t result = getpgid(pid);
48 if (result < 0)
49 {
50 fprintf(stderr, "%s\n", explain_getpgid(pid));
51 exit(EXIT_FAILURE);
52 }
53 The above code example is available pre-packaged as the
55 explain_getpgid_or_die(3) function.
56 explain_errno_getpgid
58 const char *explain_errno_getpgid(int errnum, pid_t pid);
59 The explain_errno_getpgid function is used to obtain an explanation of
61 an error returned by the getpgid(2) system call. The least the message
62 will contain is the value of strerror(errno), but usually it will do
63 much better, and indicate the underlying cause in more detail.
64 errnum The error value to be decoded, usually obtained from the errno
66 global variable just before this function is called. This is
67 necessary if you need to call any code between the system call
68 to be explained and this function, because many libc functions
69 will alter the value of errno.
70 pid The original pid, exactly as passed to the getpgid(2) system
72 call.
73 Returns:
75 The message explaining the error. This message buffer is shared
76 by all libexplain functions which do not supply a buffer in
77 their argument list. This will be overwritten by the next call
78 to any libexplain function which shares this buffer, including
79 other threads.
80 Note: This function is not thread safe, because it shares a return buf‐
82 fer across all threads, and many other functions in this library.
83 Example: This function is intended to be used in a fashion similar to
85 the following example:
86 pid_t result = getpgid(pid);
87 if (result < 0)
88 {
89 int err = errno;
90 fprintf(stderr, "%s\n", explain_errno_getpgid(err, pid));
91 exit(EXIT_FAILURE);
92 }
93 The above code example is available pre-packaged as the
95 explain_getpgid_or_die(3) function.
96 explain_message_getpgid
98 void explain_message_getpgid(char *message, int message_size, pid_t
99 pid);
100 The explain_message_getpgid function is used to obtain an explanation
102 of an error returned by the getpgid(2) system call. The least the mes‐
103 sage will contain is the value of strerror(errno), but usually it will
104 do much better, and indicate the underlying cause in more detail.
105 The errno global variable will be used to obtain the error value to be
107 decoded.
108 message The location in which to store the returned message. If a suit‐
110 able message return buffer is supplied, this function is thread
111 safe.
112 message_size
114 The size in bytes of the location in which to store the
115 returned message.
116 pid The original pid, exactly as passed to the getpgid(2) system
118 call.
119 Example: This function is intended to be used in a fashion similar to
121 the following example:
122 pid_t result = getpgid(pid);
123 if (result < 0)
124 {
125 char message[3000];
126 explain_message_getpgid(message, sizeof(message), pid);
127 fprintf(stderr, "%s\n", message);
128 exit(EXIT_FAILURE);
129 }
130 The above code example is available pre-packaged as the
132 explain_getpgid_or_die(3) function.
133 explain_message_errno_getpgid
135 void explain_message_errno_getpgid(char *message, int message_size, int
136 errnum, pid_t pid);
137 The explain_message_errno_getpgid function is used to obtain an expla‐
139 nation of an error returned by the getpgid(2) system call. The least
140 the message will contain is the value of strerror(errno), but usually
141 it will do much better, and indicate the underlying cause in more
142 detail.
143 message The location in which to store the returned message. If a suit‐
145 able message return buffer is supplied, this function is thread
146 safe.
147 message_size
149 The size in bytes of the location in which to store the
150 returned message.
151 errnum The error value to be decoded, usually obtained from the errno
153 global variable just before this function is called. This is
154 necessary if you need to call any code between the system call
155 to be explained and this function, because many libc functions
156 will alter the value of errno.
157 pid The original pid, exactly as passed to the getpgid(2) system
159 call.
160 Example: This function is intended to be used in a fashion similar to
162 the following example:
163 pid_t result = getpgid(pid);
164 if (result < 0)
165 {
166 int err = errno;
167 char message[3000];
168 explain_message_errno_getpgid(message, sizeof(message), err,
169 pid);
170 fprintf(stderr, "%s\n", message);
171 exit(EXIT_FAILURE);
172 }
173 The above code example is available pre-packaged as the
175 explain_getpgid_or_die(3) function.
176
178 getpgid(2)
179 get process group
180 explain_getpgid_or_die(3)
182 get process group and report errors
183
185 libexplain version 1.4
186 Copyright (C) 2011 Peter Miller
187 explain_getpgid(3)