1explain_vsprintf(3)        Library Functions Manual        explain_vsprintf(3)
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NAME

6       explain_vsprintf - explain vsprintf(3) errors
7

SYNOPSIS

9       #include <libexplain/vsprintf.h>
10       const char *explain_vsprintf(char *data, const char *format, va_list
11       ap);
12       const char *explain_errno_vsprintf(int errnum, char *data, const char
13       *format, va_list ap);
14       void explain_message_vsprintf(char *message, int message_size, char
15       *data, const char *format, va_list ap);
16       void explain_message_errno_vsprintf(char *message, int message_size,
17       int errnum, char *data, const char *format, va_list ap);
18

DESCRIPTION

20       These  functions may be used to obtain explanations for errors returned
21       by the vsprintf(3) system call.
22
23   explain_vsprintf
24       const char *explain_vsprintf(char *data, const char *format, va_list
25       ap);
26
27       The  explain_vsprintf  function  is used to obtain an explanation of an
28       error returned by the vsprintf(3) system call. The  least  the  message
29       will  contain  is  the value of strerror(errno), but usually it will do
30       much better, and indicate the underlying cause in more detail.
31
32       The errno global variable will be used to obtain the error value to  be
33       decoded.
34
35       data    The  original data, exactly as passed to the vsprintf(3) system
36               call.
37
38       format  The original format, exactly as passed to the vsprintf(3)  sys‐
39               tem call.
40
41       ap      The  original  ap,  exactly as passed to the vsprintf(3) system
42               call.
43
44       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
51       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
54       Example:  This  function is intended to be used in a fashion similar to
55       the following example:
56              errno = 0;
57              int result = vsprintf(data, format, ap);
58              if (result < 0 && errno != 0)
59              {
60                  fprintf(stderr, "%s\n", explain_vsprintf(data, format, ap));
61                  exit(EXIT_FAILURE);
62              }
63
64       The   above   code   example   is   available   pre‐packaged   as   the
65       explain_vsprintf_or_die(3) function.
66
67   explain_errno_vsprintf
68       const char *explain_errno_vsprintf(int errnum, char *data, const char
69       *format, va_list ap);
70
71       The explain_errno_vsprintf function is used to obtain an explanation of
72       an  error  returned by the vsprintf(3) system call.  The least the mes‐
73       sage will contain is the value of strerror(errno), but usually it  will
74       do much better, and indicate the underlying cause in more detail.
75
76       errnum  The  error value to be decoded, usually obtained from the errno
77               global variable just before this function is  called.  This  is
78               necessary  if you need to call any code between the system call
79               to be explained and this function, because many libc  functions
80               will alter the value of errno.
81
82       data    The  original data, exactly as passed to the vsprintf(3) system
83               call.
84
85       format  The original format, exactly as passed to the vsprintf(3)  sys‐
86               tem call.
87
88       ap      The  original  ap,  exactly as passed to the vsprintf(3) system
89               call.
90
91       Returns:
92               The message explaining the error. This message buffer is shared
93               by  all  libexplain  functions  which do not supply a buffer in
94               their argument list.  This will be overwritten by the next call
95               to  any libexplain function which shares this buffer, including
96               other threads.
97
98       Note: This function is not thread safe, because it shares a return buf‐
99       fer across all threads, and many other functions in this library.
100
101       Example:  This  function is intended to be used in a fashion similar to
102       the following example:
103              errno = 0;
104              int result = vsprintf(data, format, ap);
105              if (result < 0 && errno != 0)
106              {
107                  int err = errno;
108                  fprintf(stderr, "%s\n", explain_errno_vsprintf(err, data,
109                  format, ap));
110                  exit(EXIT_FAILURE);
111              }
112
113       The   above   code   example   is   available   pre‐packaged   as   the
114       explain_vsprintf_or_die(3) function.
115
116   explain_message_vsprintf
117       void explain_message_vsprintf(char *message, int message_size, char
118       *data, const char *format, va_list ap);
119
120       The  explain_message_vsprintf function is used to obtain an explanation
121       of an error returned by the vsprintf(3) system  call.   The  least  the
122       message  will  contain  is the value of strerror(errno), but usually it
123       will do much better, and indicate the underlying cause in more detail.
124
125       The errno global variable will be used to obtain the error value to  be
126       decoded.
127
128       message The location in which to store the returned message. If a suit‐
129               able message return buffer is supplied, this function is thread
130               safe.
131
132       message_size
133               The  size  in  bytes  of  the  location  in  which to store the
134               returned message.
135
136       data    The original data, exactly as passed to the vsprintf(3)  system
137               call.
138
139       format  The  original format, exactly as passed to the vsprintf(3) sys‐
140               tem call.
141
142       ap      The original ap, exactly as passed to  the  vsprintf(3)  system
143               call.
144
145       Example:  This  function is intended to be used in a fashion similar to
146       the following example:
147              errno = 0;
148              int result = vsprintf(data, format, ap);
149              if (result < 0 && errno != 0)
150              {
151                  char message[3000];
152                  explain_message_vsprintf(message, sizeof(message), data,
153                  format, ap);
154                  fprintf(stderr, "%s\n", message);
155                  exit(EXIT_FAILURE);
156              }
157
158       The   above   code   example   is   available   pre‐packaged   as   the
159       explain_vsprintf_or_die(3) function.
160
161   explain_message_errno_vsprintf
162       void explain_message_errno_vsprintf(char *message, int message_size,
163       int errnum, char *data, const char *format, va_list ap);
164
165       The explain_message_errno_vsprintf function is used to obtain an expla‐
166       nation of an error returned by the vsprintf(3) system call.  The  least
167       the  message  will contain is the value of strerror(errno), but usually
168       it will do much better, and  indicate  the  underlying  cause  in  more
169       detail.
170
171       message The location in which to store the returned message. If a suit‐
172               able message return buffer is supplied, this function is thread
173               safe.
174
175       message_size
176               The  size  in  bytes  of  the  location  in  which to store the
177               returned message.
178
179       errnum  The error value to be decoded, usually obtained from the  errno
180               global  variable  just  before this function is called. This is
181               necessary if you need to call any code between the system  call
182               to  be explained and this function, because many libc functions
183               will alter the value of errno.
184
185       data    The original data, exactly as passed to the vsprintf(3)  system
186               call.
187
188       format  The  original format, exactly as passed to the vsprintf(3) sys‐
189               tem call.
190
191       ap      The original ap, exactly as passed to  the  vsprintf(3)  system
192               call.
193
194       Example:  This  function is intended to be used in a fashion similar to
195       the following example:
196              errno = 0;
197              int result = vsprintf(data, format, ap);
198              if (result < 0 && errno != 0)
199              {
200                  int err = errno;
201                  char message[3000];
202                  explain_message_errno_vsprintf(message, sizeof(message),
203                  err, data, format, ap);
204                  fprintf(stderr, "%s\n", message);
205                  exit(EXIT_FAILURE);
206              }
207
208       The   above   code   example   is   available   pre‐packaged   as   the
209       explain_vsprintf_or_die(3) function.
210

SEE ALSO

212       vsprintf(3)
213               formatted output conversion
214
215       explain_vsprintf_or_die(3)
216               formatted output conversion and report errors
217
219       libexplain version 0.40
220       Copyright (C) 2010 Peter Miller
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224                                                           explain_vsprintf(3)
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