1explain_setpgid(3) Library Functions Manual explain_setpgid(3)
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6 explain_setpgid - explain setpgid(2) errors
7
9 #include <libexplain/setpgid.h>
10 const char *explain_setpgid(pid_t pid, pid_t pgid);
11 const char *explain_errno_setpgid(int errnum, pid_t pid, pid_t pgid);
12 void explain_message_setpgid(char *message, int message_size, pid_t
13 pid, pid_t pgid);
14 void explain_message_errno_setpgid(char *message, int message_size, int
15 errnum, pid_t pid, pid_t pgid);
16
18 These functions may be used to obtain explanations for errors returned
19 by the setpgid(2) system call.
20 explain_setpgid
22 const char *explain_setpgid(pid_t pid, pid_t pgid);
23 The explain_setpgid function is used to obtain an explanation of an
25 error returned by the setpgid(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 setpgid(2) system
33 call.
34 pgid The original pgid, exactly as passed to the setpgid(2) system
36 call.
37 Returns:
39 The message explaining the error. This message buffer is shared
40 by all libexplain functions which do not supply a buffer in
41 their argument list. This will be overwritten by the next call
42 to any libexplain function which shares this buffer, including
43 other threads.
44 Note: This function is not thread safe, because it shares a return buf‐
46 fer across all threads, and many other functions in this library.
47 Example: This function is intended to be used in a fashion similar to
49 the following example:
50 if (setpgid(pid, pgid) < 0)
51 {
52 fprintf(stderr, "%s\n", explain_setpgid(pid, pgid));
53 exit(EXIT_FAILURE);
54 }
55 The above code example is available pre-packaged as the
57 explain_setpgid_or_die(3) function.
58 explain_errno_setpgid
60 const char *explain_errno_setpgid(int errnum, pid_t pid, pid_t pgid);
61 The explain_errno_setpgid function is used to obtain an explanation of
63 an error returned by the setpgid(2) system call. The least the message
64 will contain is the value of strerror(errno), but usually it will do
65 much better, and indicate the underlying cause in more detail.
66 errnum The error value to be decoded, usually obtained from the errno
68 global variable just before this function is called. This is
69 necessary if you need to call any code between the system call
70 to be explained and this function, because many libc functions
71 will alter the value of errno.
72 pid The original pid, exactly as passed to the setpgid(2) system
74 call.
75 pgid The original pgid, exactly as passed to the setpgid(2) system
77 call.
78 Returns:
80 The message explaining the error. This message buffer is shared
81 by all libexplain functions which do not supply a buffer in
82 their argument list. This will be overwritten by the next call
83 to any libexplain function which shares this buffer, including
84 other threads.
85 Note: This function is not thread safe, because it shares a return buf‐
87 fer across all threads, and many other functions in this library.
88 Example: This function is intended to be used in a fashion similar to
90 the following example:
91 if (setpgid(pid, pgid) < 0)
92 {
93 int err = errno;
94 fprintf(stderr, "%s\n", explain_errno_setpgid(err, pid,
95 pgid));
96 exit(EXIT_FAILURE);
97 }
98 The above code example is available pre-packaged as the
100 explain_setpgid_or_die(3) function.
101 explain_message_setpgid
103 void explain_message_setpgid(char *message, int message_size, pid_t
104 pid, pid_t pgid);
105 The explain_message_setpgid function is used to obtain an explanation
107 of an error returned by the setpgid(2) system call. The least the mes‐
108 sage will contain is the value of strerror(errno), but usually it will
109 do much better, and indicate the underlying cause in more detail.
110 The errno global variable will be used to obtain the error value to be
112 decoded.
113 message The location in which to store the returned message. If a suit‐
115 able message return buffer is supplied, this function is thread
116 safe.
117 message_size
119 The size in bytes of the location in which to store the
120 returned message.
121 pid The original pid, exactly as passed to the setpgid(2) system
123 call.
124 pgid The original pgid, exactly as passed to the setpgid(2) system
126 call.
127 Example: This function is intended to be used in a fashion similar to
129 the following example:
130 if (setpgid(pid, pgid) < 0)
131 {
132 char message[3000];
133 explain_message_setpgid(message, sizeof(message), pid,
134 pgid);
135 fprintf(stderr, "%s\n", message);
136 exit(EXIT_FAILURE);
137 }
138 The above code example is available pre-packaged as the
140 explain_setpgid_or_die(3) function.
141 explain_message_errno_setpgid
143 void explain_message_errno_setpgid(char *message, int message_size, int
144 errnum, pid_t pid, pid_t pgid);
145 The explain_message_errno_setpgid function is used to obtain an expla‐
147 nation of an error returned by the setpgid(2) system call. The least
148 the message will contain is the value of strerror(errno), but usually
149 it will do much better, and indicate the underlying cause in more
150 detail.
151 message The location in which to store the returned message. If a suit‐
153 able message return buffer is supplied, this function is thread
154 safe.
155 message_size
157 The size in bytes of the location in which to store the
158 returned message.
159 errnum The error value to be decoded, usually obtained from the errno
161 global variable just before this function is called. This is
162 necessary if you need to call any code between the system call
163 to be explained and this function, because many libc functions
164 will alter the value of errno.
165 pid The original pid, exactly as passed to the setpgid(2) system
167 call.
168 pgid The original pgid, exactly as passed to the setpgid(2) system
170 call.
171 Example: This function is intended to be used in a fashion similar to
173 the following example:
174 if (setpgid(pid, pgid) < 0)
175 {
176 int err = errno;
177 char message[3000];
178 explain_message_errno_setpgid(message, sizeof(message), err,
179 pid, pgid);
180 fprintf(stderr, "%s\n", message);
181 exit(EXIT_FAILURE);
182 }
183 The above code example is available pre-packaged as the
185 explain_setpgid_or_die(3) function.
186
188 setpgid(2)
189 set process group
190 explain_setpgid_or_die(3)
192 set process group and report errors
193
195 libexplain version 1.4
196 Copyright (C) 2011 Peter Miller
197 explain_setpgid(3)