1explain_vfork(3) Library Functions Manual explain_vfork(3)
2
6 explain_vfork - explain vfork(2) errors
7
9 #include <libexplain/vfork.h>
10 const char *explain_vfork(void);
11 const char *explain_errno_vfork(int errnum, void);
12 void explain_message_vfork(char *message, int message_size, void);
13 void explain_message_errno_vfork(char *message, int message_size, int
14 errnum, void);
15
17 These functions may be used to obtain explanations for errors returned
18 by the vfork(2) system call.
19 explain_vfork
21 const char *explain_vfork(void);
22 The explain_vfork function is used to obtain an explanation of an error
24 returned by the vfork(2) system call. The least the message will con‐
25 tain is the value of strerror(errno), but usually it will do much bet‐
26 ter, and indicate the underlying cause in more detail.
27 The errno global variable will be used to obtain the error value to be
29 decoded.
30 Returns:
32 The message explaining the error. This message buffer is shared
33 by all libexplain functions which do not supply a buffer in
34 their argument list. This will be overwritten by the next call
35 to any libexplain function which shares this buffer, including
36 other threads.
37 Note: This function is not thread safe, because it shares a return buf‐
39 fer across all threads, and many other functions in this library.
40 Example: This function is intended to be used in a fashion similar to
42 the following example:
43 pid_t result = vfork();
44 if (result < 0)
45 {
46 fprintf(stderr, "%s\n", explain_vfork());
47 exit(EXIT_FAILURE);
48 }
49 The above code example is available pre‐packaged as the
51 explain_vfork_or_die(3) function.
52 explain_errno_vfork
54 const char *explain_errno_vfork(int errnum, void);
55 The explain_errno_vfork function is used to obtain an explanation of an
57 error returned by the vfork(2) system call. The least the message will
58 contain is the value of strerror(errno), but usually it will do much
59 better, and indicate the underlying cause in more detail.
60 errnum The error value to be decoded, usually obtained from the errno
62 global variable just before this function is called. This is
63 necessary if you need to call any code between the system call
64 to be explained and this function, because many libc functions
65 will alter the value of errno.
66 Returns:
68 The message explaining the error. This message buffer is shared
69 by all libexplain functions which do not supply a buffer in
70 their argument list. This will be overwritten by the next call
71 to any libexplain function which shares this buffer, including
72 other threads.
73 Note: This function is not thread safe, because it shares a return buf‐
75 fer across all threads, and many other functions in this library.
76 Example: This function is intended to be used in a fashion similar to
78 the following example:
79 pid_t result = vfork();
80 if (result < 0)
81 {
82 int err = errno;
83 fprintf(stderr, "%s\n", explain_errno_vfork(err, ));
84 exit(EXIT_FAILURE);
85 }
86 The above code example is available pre‐packaged as the
88 explain_vfork_or_die(3) function.
89 explain_message_vfork
91 void explain_message_vfork(char *message, int message_size, void);
92 The explain_message_vfork function is used to obtain an explanation of
94 an error returned by the vfork(2) system call. The least the message
95 will contain is the value of strerror(errno), but usually it will do
96 much better, and indicate the underlying cause in more detail.
97 The errno global variable will be used to obtain the error value to be
99 decoded.
100 message The location in which to store the returned message. If a suit‐
102 able message return buffer is supplied, this function is thread
103 safe.
104 message_size
106 The size in bytes of the location in which to store the
107 returned message.
108 Example: This function is intended to be used in a fashion similar to
110 the following example:
111 pid_t result = vfork();
112 if (result < 0)
113 {
114 char message[3000];
115 explain_message_vfork(message, sizeof(message), );
116 fprintf(stderr, "%s\n", message);
117 exit(EXIT_FAILURE);
118 }
119 The above code example is available pre‐packaged as the
121 explain_vfork_or_die(3) function.
122 explain_message_errno_vfork
124 void explain_message_errno_vfork(char *message, int message_size, int
125 errnum, void);
126 The explain_message_errno_vfork function is used to obtain an explana‐
128 tion of an error returned by the vfork(2) system call. The least the
129 message will contain is the value of strerror(errno), but usually it
130 will do much better, and indicate the underlying cause in more detail.
131 message The location in which to store the returned message. If a suit‐
133 able message return buffer is supplied, this function is thread
134 safe.
135 message_size
137 The size in bytes of the location in which to store the
138 returned message.
139 errnum The error value to be decoded, usually obtained from the errno
141 global variable just before this function is called. This is
142 necessary if you need to call any code between the system call
143 to be explained and this function, because many libc functions
144 will alter the value of errno.
145 Example: This function is intended to be used in a fashion similar to
147 the following example:
148 pid_t result = vfork();
149 if (result < 0)
150 {
151 int err = errno;
152 char message[3000];
153 explain_message_errno_vfork(message, sizeof(message), err,
154 );
155 fprintf(stderr, "%s\n", message);
156 exit(EXIT_FAILURE);
157 }
158 The above code example is available pre‐packaged as the
160 explain_vfork_or_die(3) function.
161
163 vfork(2)
164 create a child process and block parent
165 explain_vfork_or_die(3)
167 create a child process and block parent and report errors
168
170 libexplain version 1.4
171 Copyright (C) 2009 Peter Miller
172 explain_vfork(3)