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

6       explain_fgets - explain fgets(3) errors
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SYNOPSIS

9       #include <libexplain/fgets.h>
10       const char *explain_fgets(char *data, int data_size, FILE *fp);
11       const  char *explain_errno_fgets(int errnum, char *data, int data_size,
12       FILE *fp);
13       void explain_message_fgets(char *message, int message_size, char *data,
14       int data_size, FILE *fp);
15       void  explain_message_errno_fgets(char  *message, int message_size, int
16       errnum, char *data, int data_size, FILE *fp);
17

DESCRIPTION

19       These functions may be used to obtain explanations for errors  returned
20       by the fgets(3) system call.
21
22   explain_fgets
23       const char *explain_fgets(char *data, int data_size, FILE *fp);
24
25       The explain_fgets function is used to obtain an explanation of an error
26       returned by the fgets(3) system call.  The least the message will  con‐
27       tain  is the value of strerror(errno), but usually it will do much bet‐
28       ter, and indicate the underlying cause in more detail.
29
30       The errno global variable will be used to obtain the error value to  be
31       decoded.
32
33       This  function  is intended to be used in a fashion similar to the fol‐
34       lowing example:
35              if (fgets(data, data_size, fp) < 0)
36              {
37                  fprintf(stderr, "%s\n", explain_fgets(data, data_size, fp));
38                  exit(EXIT_FAILURE);
39              }
40
41       data    The original data, exactly as passed  to  the  fgets(3)  system
42               call.
43
44       data_size
45               The  original data_size, exactly as passed to the fgets(3) sys‐
46               tem call.
47
48       fp      The original fp, exactly as passed to the fgets(3) system call.
49
50       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
57       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
60   explain_errno_fgets
61       const  char *explain_errno_fgets(int errnum, char *data, int data_size,
62       FILE *fp);
63
64       The explain_errno_fgets function is used to obtain an explanation of an
65       error returned by the fgets(3) system call.  The least the message will
66       contain is the value of strerror(errnum), but usually it will  do  much
67       better, and indicate the underlying cause in more detail.
68
69       This  function  is intended to be used in a fashion similar to the fol‐
70       lowing example:
71              if (fgets(data, data_size, fp) < 0)
72              {
73                  int err = errno;
74                  fprintf(stderr, "%s\n", explain_errno_fgets(err, data, data_size, fp));
75                  exit(EXIT_FAILURE);
76              }
77
78       errnum  The error value to be decoded, usually obtained from the  errno
79               global  variable  just before this function is called.  This is
80               necessary if you need to call any code between the system  call
81               to  be explained and this function, because many libc functions
82               will alter the value of errno.
83
84       data    The original data, exactly as passed  to  the  fgets(3)  system
85               call.
86
87       data_size
88               The  original data_size, exactly as passed to the fgets(3) sys‐
89               tem call.
90
91       fp      The original fp, exactly as passed to the fgets(3) system call.
92
93       Returns:
94               The message explaining  the  error.   This  message  buffer  is
95               shared by all libexplain functions which do not supply a buffer
96               in their argument list.  This will be overwritten by  the  next
97               call  to  any  libexplain  function  which  shares this buffer,
98               including other threads.
99
100       Note: This function is not thread safe, because it shares a return buf‐
101       fer across all threads, and many other functions in this library.
102
103   explain_message_fgets
104       void explain_message_fgets(char *message, int message_size, char *data,
105       int data_size, FILE *fp);
106
107       The explain_message_fgets function may be used to  obtain  an  explana‐
108       tion  of  an error returned by the fgets(3) system call.  The least the
109       message will contain is the value of strerror(errno),  but  usually  it
110       will do much better, and indicate the underlying cause in more detail.
111
112       The  errno global variable will be used to obtain the error value to be
113       decoded.
114
115       This function is intended to be used in a fashion similar to  the  fol‐
116       lowing example:
117              if (fgets(data, data_size, fp) < 0)
118              {
119                  char message[3000];
120                  explain_message_fgets(message, sizeof(message), data, data_size, fp);
121                  fprintf(stderr, "%s\n", message);
122                  exit(EXIT_FAILURE);
123              }
124
125       message The  location  in  which  to  store the returned message.  If a
126               suitable message return buffer is supplied,  this  function  is
127               thread safe.
128
129       message_size
130               The  size  in  bytes  of  the  location  in  which to store the
131               returned message.
132
133       data    The original data, exactly as passed  to  the  fgets(3)  system
134               call.
135
136       data_size
137               The  original data_size, exactly as passed to the fgets(3) sys‐
138               tem call.
139
140       fp      The original fp, exactly as passed to the fgets(3) system call.
141
142   explain_message_errno_fgets
143       void explain_message_errno_fgets(char *message, int  message_size,  int
144       errnum, char *data, int data_size, FILE *fp);
145
146       The  explain_message_errno_fgets  function  may  be  used  to obtain an
147       explanation of an error returned by  the  fgets(3)  system  call.   The
148       least  the  message  will contain is the value of strerror(errnum), but
149       usually it will do much better, and indicate the  underlying  cause  in
150       more detail.
151
152       This  function  is intended to be used in a fashion similar to the fol‐
153       lowing example:
154              if (fgets(data, data_size, fp) < 0)
155              {
156                  int err = errno;
157                  char message[3000];
158                  explain_message_errno_fgets(message, sizeof(message), err,
159                      data, data_size, fp);
160                  fprintf(stderr, "%s\n", message);
161                  exit(EXIT_FAILURE);
162              }
163
164       message The location in which to store  the  returned  message.   If  a
165               suitable  message  return  buffer is supplied, this function is
166               thread safe.
167
168       message_size
169               The size in bytes  of  the  location  in  which  to  store  the
170               returned message.
171
172       errnum  The  error value to be decoded, usually obtained from the errno
173               global variable just before this function is called.   This  is
174               necessary  if you need to call any code between the system call
175               to be explained and this function, because many libc  functions
176               will alter the value of errno.
177
178       data    The  original  data,  exactly  as passed to the fgets(3) system
179               call.
180
181       data_size
182               The original data_size, exactly as passed to the fgets(3)  sys‐
183               tem call.
184
185       fp      The original fp, exactly as passed to the fgets(3) system call.
186

SEE ALSO

188       fgets(3)
189               input of strings
190
191       explain_fgets_or_die(3)
192               input of strings and report errors
193
195       libexplain version 0.40
196       Copyright (C) 2008 Peter Miller
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200                                                              explain_fgets(3)
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