1explain_ftruncate(3) Library Functions Manual explain_ftruncate(3)
2
6 explain_ftruncate - explain ftruncate(2) errors
7
9 #include <libexplain/ftruncate.h>
10 const char *explain_ftruncate(int fildes, long long length);
11 const char *explain_errno_ftruncate(int errnum, int fildes, long long
12 length);
13 void explain_message_ftruncate(char *message, int message_size, int
14 fildes, long long length);
15 void explain_message_errno_ftruncate(char *message, int message_size,
16 int errnum, int fildes, long long length);
17
19 These functions may be used to obtain explanations for errors returned
20 by the ftruncate(2) system call.
21 explain_ftruncate
23 const char *explain_ftruncate(int fildes, long long length);
24 The explain_ftruncate function is used to obtain an explanation of an
26 error returned by the ftruncate(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 (ftruncate(fildes, length) < 0)
36 {
37 fprintf(stderr, "%s\n", explain_ftruncate(fildes, length));
38 exit(EXIT_FAILURE);
39 }
40 fildes The original fildes, exactly as passed to the ftruncate(2) sys‐
42 tem call.
43 length The original length, exactly as passed to the ftruncate(2) sys‐
45 tem call.
46 Returns:
48 The message explaining the error. This message buffer is
49 shared by all libexplain functions which do not supply a buffer
50 in their argument list. This will be overwritten by the next
51 call to any libexplain function which shares this buffer,
52 including other threads.
53 Note: This function is not thread safe, because it shares a return buf‐
55 fer across all threads, and many other functions in this library.
56 explain_errno_ftruncate
58 const char *explain_errno_ftruncate(int errnum, int fildes, long long
59 length);
60 The explain_errno_ftruncate function is used to obtain an explanation
62 of an error returned by the ftruncate(2) system call. The least the
63 message will contain is the value of strerror(errnum), but usually it
64 will do much better, and indicate the underlying cause in more detail.
65 This function is intended to be used in a fashion similar to the fol‐
67 lowing example:
68 if (ftruncate(fildes, length) < 0)
69 {
70 int err = errno;
71 fprintf(stderr, "%s\n", explain_errno_ftruncate(err, fildes, length));
72 exit(EXIT_FAILURE);
73 }
74 errnum The error value to be decoded, usually obtained from the errno
76 global variable just before this function is called. This is
77 necessary if you need to call any code between the system call
78 to be explained and this function, because many libc functions
79 will alter the value of errno.
80 fildes The original fildes, exactly as passed to the ftruncate(2) sys‐
82 tem call.
83 length The original length, exactly as passed to the ftruncate(2) sys‐
85 tem call.
86 Returns:
88 The message explaining the error. This message buffer is
89 shared by all libexplain functions which do not supply a buffer
90 in their argument list. This will be overwritten by the next
91 call to any libexplain function which shares this buffer,
92 including other threads.
93 Note: This function is not thread safe, because it shares a return buf‐
95 fer across all threads, and many other functions in this library.
96 explain_message_ftruncate
98 void explain_message_ftruncate(char *message, int message_size, int
99 fildes, long long length);
100 The explain_message_ftruncate function may be used to obtain an expla‐
102 nation of an error returned by the ftruncate(2) system call. The least
103 the message will contain is the value of strerror(errno), but usually
104 it will do much better, and indicate the underlying cause in more
105 detail.
106 The errno global variable will be used to obtain the error value to be
108 decoded.
109 This function is intended to be used in a fashion similar to the fol‐
111 lowing example:
112 if (ftruncate(fildes, length) < 0)
113 {
114 char message[3000];
115 explain_message_ftruncate(message, sizeof(message), fildes, length);
116 fprintf(stderr, "%s\n", message);
117 exit(EXIT_FAILURE);
118 }
119 message The location in which to store the returned message. If a
121 suitable message return buffer is supplied, this function is
122 thread safe.
123 message_size
125 The size in bytes of the location in which to store the
126 returned message.
127 fildes The original fildes, exactly as passed to the ftruncate(2) sys‐
129 tem call.
130 length The original length, exactly as passed to the ftruncate(2) sys‐
132 tem call.
133 explain_message_errno_ftruncate
135 void explain_message_errno_ftruncate(char *message, int message_size,
136 int errnum, int fildes, long long length);
137 The explain_message_errno_ftruncate function may be used to obtain an
139 explanation of an error returned by the ftruncate(2) system call. The
140 least the message will contain is the value of strerror(errnum), but
141 usually it will do much better, and indicate the underlying cause in
142 more detail.
143 This function is intended to be used in a fashion similar to the fol‐
145 lowing example:
146 if (ftruncate(fildes, length) < 0)
147 {
148 int err = errno;
149 char message[3000];
150 explain_message_errno_ftruncate(message, sizeof(message), err,
151 fildes, length);
152 fprintf(stderr, "%s\n", message);
153 exit(EXIT_FAILURE);
154 }
155 message The location in which to store the returned message. If a
157 suitable message return buffer is supplied, this function is
158 thread safe.
159 message_size
161 The size in bytes of the location in which to store the
162 returned message.
163 errnum The error value to be decoded, usually obtained from the errno
165 global variable just before this function is called. This is
166 necessary if you need to call any code between the system call
167 to be explained and this function, because many libc functions
168 will alter the value of errno.
169 fildes The original fildes, exactly as passed to the ftruncate(2) sys‐
171 tem call.
172 length The original length, exactly as passed to the ftruncate(2) sys‐
174 tem call.
175
177 ftruncate(2)
178 truncate a file to a specified length
179 explain_ftruncate_or_die(3)
181 truncate a file and report errors
182
184 libexplain version 1.4
185 Copyright (C) 2008 Peter Miller
186 explain_ftruncate(3)