1explain_fchmod(3) Library Functions Manual explain_fchmod(3)
2
6 explain_fchmod - explain fchmod(2) errors
7
9 #include <libexplain/fchmod.h>
10 const char *explain_fchmod(int fildes, mode_t mode);
11 const char *explain_errno_fchmod(int errnum, int fildes, mode_t mode);
12 void explain_message_fchmod(char *message, int message_size, int
13 fildes, mode_t mode);
14 void explain_message_errno_fchmod(char *message, int message_size, int
15 errnum, int fildes, mode_t mode);
16
18 These functions may be used to obtain explanations for errors returned
19 by the fchmod(2) system call.
20 explain_fchmod
22 const char *explain_fchmod(int fildes, mode_t mode);
23 The explain_fchmod function is used to obtain an explanation of an
25 error returned by the fchmod(2) system call. The least the message will
26 contain is the value of strerror(errno), but usually it will do much
27 better, and indicate the underlying cause in more detail.
28 The errno global variable will be used to obtain the error value to be
30 decoded.
31 fildes The original fildes, exactly as passed to the fchmod(2) system
33 call.
34 mode The original mode, exactly as passed to the fchmod(2) system
36 call.
37 Returns:
39 The message explaining the error. This message buffer is shared
40 by all libexplain functions which do not supply a buffer in
41 their argument list. This will be overwritten by the next call
42 to any libexplain function which shares this buffer, including
43 other threads.
44 Note: This function is not thread safe, because it shares a return buf‐
46 fer across all threads, and many other functions in this library.
47 Example: This function is intended to be used in a fashion similar to
49 the following example:
50 if (fchmod(fildes, mode) < 0)
51 {
52 fprintf(stderr, "%s\n", explain_fchmod(fildes, mode));
53 exit(EXIT_FAILURE);
54 }
55 The above code example is available pre-packaged as the explain_fch‐
57 mod_or_die(3) function.
58 explain_errno_fchmod
60 const char *explain_errno_fchmod(int errnum, int fildes, mode_t mode);
61 The explain_errno_fchmod function is used to obtain an explanation of
63 an error returned by the fchmod(2) system call. The least the message
64 will contain is the value of strerror(errno), but usually it will do
65 much better, and indicate the underlying cause in more detail.
66 errnum The error value to be decoded, usually obtained from the errno
68 global variable just before this function is called. This is
69 necessary if you need to call any code between the system call
70 to be explained and this function, because many libc functions
71 will alter the value of errno.
72 fildes The original fildes, exactly as passed to the fchmod(2) system
74 call.
75 mode The original mode, exactly as passed to the fchmod(2) system
77 call.
78 Returns:
80 The message explaining the error. This message buffer is shared
81 by all libexplain functions which do not supply a buffer in
82 their argument list. This will be overwritten by the next call
83 to any libexplain function which shares this buffer, including
84 other threads.
85 Note: This function is not thread safe, because it shares a return buf‐
87 fer across all threads, and many other functions in this library.
88 Example: This function is intended to be used in a fashion similar to
90 the following example:
91 if (fchmod(fildes, mode) < 0)
92 {
93 int err = errno;
94 fprintf(stderr, "%s\n", explain_errno_fchmod(err, fildes,
95 mode));
96 exit(EXIT_FAILURE);
97 }
98 The above code example is available pre-packaged as the explain_fch‐
100 mod_or_die(3) function.
101 explain_message_fchmod
103 void explain_message_fchmod(char *message, int message_size, int
104 fildes, mode_t mode);
105 The explain_message_fchmod function is used to obtain an explanation of
107 an error returned by the fchmod(2) system call. The least the message
108 will contain is the value of strerror(errno), but usually it will do
109 much better, and indicate the underlying cause in more detail.
110 The errno global variable will be used to obtain the error value to be
112 decoded.
113 message The location in which to store the returned message. If a suit‐
115 able message return buffer is supplied, this function is thread
116 safe.
117 message_size
119 The size in bytes of the location in which to store the
120 returned message.
121 fildes The original fildes, exactly as passed to the fchmod(2) system
123 call.
124 mode The original mode, exactly as passed to the fchmod(2) system
126 call.
127 Example: This function is intended to be used in a fashion similar to
129 the following example:
130 if (fchmod(fildes, mode) < 0)
131 {
132 char message[3000];
133 explain_message_fchmod(message, sizeof(message), fildes,
134 mode);
135 fprintf(stderr, "%s\n", message);
136 exit(EXIT_FAILURE);
137 }
138 The above code example is available pre-packaged as the explain_fch‐
140 mod_or_die(3) function.
141 explain_message_errno_fchmod
143 void explain_message_errno_fchmod(char *message, int message_size, int
144 errnum, int fildes, mode_t mode);
145 The explain_message_errno_fchmod function is used to obtain an explana‐
147 tion of an error returned by the fchmod(2) system call. The least the
148 message will contain is the value of strerror(errno), but usually it
149 will do much better, and indicate the underlying cause in more detail.
150 message The location in which to store the returned message. If a suit‐
152 able message return buffer is supplied, this function is thread
153 safe.
154 message_size
156 The size in bytes of the location in which to store the
157 returned message.
158 errnum The error value to be decoded, usually obtained from the errno
160 global variable just before this function is called. This is
161 necessary if you need to call any code between the system call
162 to be explained and this function, because many libc functions
163 will alter the value of errno.
164 fildes The original fildes, exactly as passed to the fchmod(2) system
166 call.
167 mode The original mode, exactly as passed to the fchmod(2) system
169 call.
170 Example: This function is intended to be used in a fashion similar to
172 the following example:
173 if (fchmod(fildes, mode) < 0)
174 {
175 int err = errno;
176 char message[3000];
177 explain_message_errno_fchmod(message, sizeof(message), err,
178 fildes, mode);
179 fprintf(stderr, "%s\n", message);
180 exit(EXIT_FAILURE);
181 }
182 The above code example is available pre-packaged as the explain_fch‐
184 mod_or_die(3) function.
185
187 fchmod(2)
188 change permissions of an open file
189 explain_fchmod_or_die(3)
191 change permissions of an open file and report errors
192
194 libexplain version 1.4
195 Copyright (C) 2013 Peter Miller
196 explain_fchmod(3)