1explain_waitpid(3) Library Functions Manual explain_waitpid(3)
2
6 explain_waitpid - explain waitpid(2) errors
7
9 #include <libexplain/waitpid.h>
10 const char *explain_waitpid(int pid, int *status, int options);
11 const char *explain_errno_waitpid(int errnum, int pid, int *status, int
12 options);
13 void explain_message_waitpid(char *message, int message_size, int pid,
14 int *status, int options);
15 void explain_message_errno_waitpid(char *message, int message_size, int
16 errnum, int pid, int *status, int options);
17
19 These functions may be used to obtain explanations for errors returned
20 by the waitpid(2) system call.
21 explain_waitpid
23 const char *explain_waitpid(int pid, int *status, int options);
24 The explain_waitpid function is used to obtain an explanation of an
26 error returned by the waitpid(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 The errno global variable will be used to obtain the error value to be
31 decoded.
32 This function is intended to be used in a fashion similar to the fol‐
34 lowing example:
35 if (waitpid(pid, status, options) < 0)
36 {
37 fprintf(stderr, "%s\n", explain_waitpid(pid, status, options));
38 exit(EXIT_FAILURE);
39 }
40 pid The original pid, exactly as passed to the waitpid(2) system
42 call.
43 status The original status, exactly as passed to the waitpid(2) system
45 call.
46 options The original options, exactly as passed to the waitpid(2) sys‐
48 tem call.
49 Returns:
51 The message explaining the error. This message buffer is
52 shared by all libexplain functions which do not supply a buffer
53 in their argument list. This will be overwritten by the next
54 call to any libexplain function which shares this buffer,
55 including other threads.
56 Note: This function is not thread safe, because it shares a return buf‐
58 fer across all threads, and many other functions in this library.
59 explain_errno_waitpid
61 const char *explain_errno_waitpid(int errnum, int pid, int *status, int
62 options);
63 The explain_errno_waitpid function is used to obtain an explanation of
65 an error returned by the waitpid(2) system call. The least the message
66 will contain is the value of strerror(errnum), but usually it will do
67 much better, and indicate the underlying cause in more detail.
68 This function is intended to be used in a fashion similar to the fol‐
70 lowing example:
71 if (waitpid(pid, status, options) < 0)
72 {
73 int err = errno;
74 fprintf(stderr, "%s\n", explain_errno_waitpid(err,
75 pid, status, options));
76 exit(EXIT_FAILURE);
77 }
78 errnum The error value to be decoded, usually obtained from the errno
80 global variable just before this function is called. This is
81 necessary if you need to call any code between the system call
82 to be explained and this function, because many libc functions
83 will alter the value of errno.
84 pid The original pid, exactly as passed to the waitpid(2) system
86 call.
87 status The original status, exactly as passed to the waitpid(2) system
89 call.
90 options The original options, exactly as passed to the waitpid(2) sys‐
92 tem call.
93 Returns:
95 The message explaining the error. This message buffer is
96 shared by all libexplain functions which do not supply a buffer
97 in their argument list. This will be overwritten by the next
98 call to any libexplain function which shares this buffer,
99 including other threads.
100 Note: This function is not thread safe, because it shares a return buf‐
102 fer across all threads, and many other functions in this library.
103 explain_message_waitpid
105 void explain_message_waitpid(char *message, int message_size, int pid,
106 int *status, int options);
107 The explain_message_waitpid function may be used to obtain an explana‐
109 tion of an error returned by the waitpid(2) system call. The least the
110 message will contain is the value of strerror(errno), but usually it
111 will do much better, and indicate the underlying cause in more detail.
112 The errno global variable will be used to obtain the error value to be
114 decoded.
115 This function is intended to be used in a fashion similar to the fol‐
117 lowing example:
118 if (waitpid(pid, status, options) < 0)
119 {
120 char message[3000];
121 explain_message_waitpid(message, sizeof(message), pid, status, options);
122 fprintf(stderr, "%s\n", message);
123 exit(EXIT_FAILURE);
124 }
125 message The location in which to store the returned message. If a
127 suitable message return buffer is supplied, this function is
128 thread safe.
129 message_size
131 The size in bytes of the location in which to store the
132 returned message.
133 pid The original pid, exactly as passed to the waitpid(2) system
135 call.
136 status The original status, exactly as passed to the waitpid(2) system
138 call.
139 options The original options, exactly as passed to the waitpid(2) sys‐
141 tem call.
142 explain_message_errno_waitpid
144 void explain_message_errno_waitpid(char *message, int message_size, int
145 errnum, int pid, int *status, int options);
146 The explain_message_errno_waitpid function may be used to obtain an
148 explanation of an error returned by the waitpid(2) system call. The
149 least the message will contain is the value of strerror(errnum), but
150 usually it will do much better, and indicate the underlying cause in
151 more detail.
152 This function is intended to be used in a fashion similar to the fol‐
154 lowing example:
155 if (waitpid(pid, status, options) < 0)
156 {
157 int err = errno;
158 char message[3000];
159 explain_message_errno_waitpid(message, sizeof(message), err,
160 pid, status, options);
161 fprintf(stderr, "%s\n", message);
162 exit(EXIT_FAILURE);
163 }
164 message The location in which to store the returned message. If a
166 suitable message return buffer is supplied, this function is
167 thread 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 pid The original pid, exactly as passed to the waitpid(2) system
180 call.
181 status The original status, exactly as passed to the waitpid(2) system
183 call.
184 options The original options, exactly as passed to the waitpid(2) sys‐
186 tem call.
187
189 waitpid(2)
190 wait for process to change state
191 explain_waitpid_or_die(3)
193 wait for process to change state and report errors
194
196 libexplain version 1.4
197 Copyright (C) 2008 Peter Miller
198 explain_waitpid(3)