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

6       explain_fileno - explain fileno(3) errors
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SYNOPSIS

9       #include <libexplain/fileno.h>
10       const char *explain_fileno(FILE *fp);
11       const char *explain_errno_fileno(int errnum, FILE *fp);
12       void explain_message_fileno(char *message, int message_size, FILE *fp);
13       void explain_message_errno_fileno(char *message, int message_size, int
14       errnum, FILE *fp);
15

DESCRIPTION

17       These functions may be used to obtain explanations for errors  returned
18       by the fileno(3) system call.
19
20   explain_fileno
21       const char *explain_fileno(FILE *fp);
22
23       The  explain_fileno  function  is  used  to obtain an explanation of an
24       error returned by the fileno(3) system call. The least the message will
25       contain  is  the  value of strerror(errno), but usually it will do much
26       better, and indicate the underlying cause in more detail.
27
28       The errno global variable will be used to obtain the error value to  be
29       decoded.
30
31       fp      The  original  fp,  exactly  as  passed to the fileno(3) system
32               call.
33
34       Returns:
35               The message explaining the error. This message buffer is shared
36               by  all  libexplain  functions  which do not supply a buffer in
37               their argument list.  This will be overwritten by the next call
38               to  any libexplain function which shares this buffer, including
39               other threads.
40
41       Note: This function is not thread safe, because it shares a return buf‐
42       fer across all threads, and many other functions in this library.
43
44       Example:  This  function is intended to be used in a fashion similar to
45       the following example:
46              if (fileno(fp) < 0)
47              {
48                  fprintf(stderr, "%s\n", explain_fileno(fp));
49                  exit(EXIT_FAILURE);
50              }
51
52       The   above   code   example   is   available   pre‐packaged   as   the
53       explain_fileno_or_die(3) function.
54
55   explain_errno_fileno
56       const char *explain_errno_fileno(int errnum, FILE *fp);
57
58       The  explain_errno_fileno  function is used to obtain an explanation of
59       an error returned by the fileno(3) system call. The least  the  message
60       will  contain  is  the value of strerror(errno), but usually it will do
61       much better, and indicate the underlying cause in more detail.
62
63       errnum  The error value to be decoded, usually obtained from the  errno
64               global  variable  just  before this function is called. This is
65               necessary if you need to call any code between the system  call
66               to  be explained and this function, because many libc functions
67               will alter the value of errno.
68
69       fp      The original fp, exactly as  passed  to  the  fileno(3)  system
70               call.
71
72       Returns:
73               The message explaining the error. This message buffer is shared
74               by all libexplain functions which do not  supply  a  buffer  in
75               their argument list.  This will be overwritten by the next call
76               to any libexplain function which shares this buffer,  including
77               other threads.
78
79       Note: This function is not thread safe, because it shares a return buf‐
80       fer across all threads, and many other functions in this library.
81
82       Example: This function is intended to be used in a fashion  similar  to
83       the following example:
84              if (fileno(fp) < 0)
85              {
86                  int err = errno;
87                  fprintf(stderr, "%s\n", explain_errno_fileno(err, fp));
88                  exit(EXIT_FAILURE);
89              }
90
91       The   above   code   example   is   available   pre‐packaged   as   the
92       explain_fileno_or_die(3) function.
93
94   explain_message_fileno
95       void explain_message_fileno(char *message, int message_size, FILE *fp);
96
97       The explain_message_fileno function is used to obtain an explanation of
98       an  error  returned by the fileno(3) system call. The least the message
99       will contain is the value of strerror(errno), but usually  it  will  do
100       much better, and indicate the underlying cause in more detail.
101
102       The  errno global variable will be used to obtain the error value to be
103       decoded.
104
105       message The location in which to store the returned message. If a suit‐
106               able message return buffer is supplied, this function is thread
107               safe.
108
109       message_size
110               The size in bytes  of  the  location  in  which  to  store  the
111               returned message.
112
113       fp      The  original  fp,  exactly  as  passed to the fileno(3) system
114               call.
115
116       Example: This function is intended to be used in a fashion  similar  to
117       the following example:
118              if (fileno(fp) < 0)
119              {
120                  char message[3000];
121                  explain_message_fileno(message, sizeof(message), fp);
122                  fprintf(stderr, "%s\n", message);
123                  exit(EXIT_FAILURE);
124              }
125
126       The   above   code   example   is   available   pre‐packaged   as   the
127       explain_fileno_or_die(3) function.
128
129   explain_message_errno_fileno
130       void explain_message_errno_fileno(char *message, int message_size, int
131       errnum, FILE *fp);
132
133       The explain_message_errno_fileno function is used to obtain an explana‐
134       tion of an error returned by the fileno(3) system call. The  least  the
135       message  will  contain  is the value of strerror(errno), but usually it
136       will do much better, and indicate the underlying cause in more detail.
137
138       message The location in which to store the returned message. If a suit‐
139               able message return buffer is supplied, this function is thread
140               safe.
141
142       message_size
143               The size in bytes  of  the  location  in  which  to  store  the
144               returned message.
145
146       errnum  The  error value to be decoded, usually obtained from the errno
147               global variable just before this function is  called.  This  is
148               necessary  if you need to call any code between the system call
149               to be explained and this function, because many libc  functions
150               will alter the value of errno.
151
152       fp      The  original  fp,  exactly  as  passed to the fileno(3) system
153               call.
154
155       Example: This function is intended to be used in a fashion  similar  to
156       the following example:
157              if (fileno(fp) < 0)
158              {
159                  int err = errno;
160                  char message[3000];
161                  explain_message_errno_fileno(message, sizeof(message), err,
162                  fp);
163                  fprintf(stderr, "%s\n", message);
164                  exit(EXIT_FAILURE);
165              }
166
167       The   above   code   example   is   available   pre‐packaged   as   the
168       explain_fileno_or_die(3) function.
169

SEE ALSO

171       fileno(3)
172               check and reset stream status
173
174       explain_fileno_or_die(3)
175               check and reset stream status and report errors
176
178       libexplain version 0.40
179       Copyright (C) 2009 Peter Miller
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183                                                             explain_fileno(3)
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