1explain_system(3) Library Functions Manual explain_system(3)
2
6 explain_system - explain system(3) errors
7
9 #include <libexplain/system.h>
10 const char *explain_system(const char *command);
11 const char *explain_errno_system(int errnum, const char *command);
12 void explain_message_system(char *message, int message_size, const char
13 *command);
14 void explain_message_errno_system(char *message, int message_size, int
15 errnum, const char *command);
16
18 These functions may be used to obtain explanations for errors returned
19 by the system(3) system call.
20 explain_system
22 const char *explain_system(const char *command);
23 The explain_system function is used to obtain an explanation of an
25 error returned by the system(3) system call. The least the message
26 will contain is the value of strerror(errno), but usually it will do
27 much 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 This function is intended to be used in a fashion similar to the fol‐
33 lowing example:
34 if (system(command) < 0)
35 {
36 fprintf(stderr, "%s\n", explain_system(command));
37 exit(EXIT_FAILURE);
38 }
39 command The original command, exactly as passed to the system(3) system
41 call.
42 Returns:
44 The message explaining the error. This message buffer is
45 shared by all libexplain functions which do not supply a buffer
46 in their argument list. This will be overwritten by the next
47 call to any libexplain function which shares this buffer,
48 including other threads.
49 Note: This function is not thread safe, because it shares a return buf‐
51 fer across all threads, and many other functions in this library.
52 explain_errno_system
54 const char *explain_errno_system(int errnum, const char *command);
55 The explain_errno_system function is used to obtain an explanation of
57 an error returned by the system(3) system call. The least the message
58 will contain is the value of strerror(errnum), but usually it will do
59 much better, and indicate the underlying cause in more detail.
60 This function is intended to be used in a fashion similar to the fol‐
62 lowing example:
63 if (system(command) < 0)
64 {
65 int err = errno;
66 fprintf(stderr, "%s\n", explain_errno_system(err, command));
67 exit(EXIT_FAILURE);
68 }
69 errnum The error value to be decoded, usually obtained from the errno
71 global variable just before this function is called. This is
72 necessary if you need to call any code between the system call
73 to be explained and this function, because many libc functions
74 will alter the value of errno.
75 command The original command, exactly as passed to the system(3) system
77 call.
78 Returns:
80 The message explaining the error. This message buffer is
81 shared by all libexplain functions which do not supply a buffer
82 in their argument list. This will be overwritten by the next
83 call to any libexplain function which shares this buffer,
84 including 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 explain_message_system
90 void explain_message_system(char *message, int message_size, const char
91 *command);
92 The explain_message_system function may be used to obtain an explana‐
94 tion of an error returned by the system(3) system call. The least the
95 message will contain is the value of strerror(errno), but usually it
96 will do much better, and indicate the underlying cause in more detail.
97 The errno global variable will be used to obtain the error value to be
99 decoded.
100 This function is intended to be used in a fashion similar to the fol‐
102 lowing example:
103 if (system(command) < 0)
104 {
105 char message[3000];
106 explain_message_system(message, sizeof(message), command);
107 fprintf(stderr, "%s\n", message);
108 exit(EXIT_FAILURE);
109 }
110 message The location in which to store the returned message. If a
112 suitable message return buffer is supplied, this function is
113 thread safe.
114 message_size
116 The size in bytes of the location in which to store the
117 returned message.
118 command The original command, exactly as passed to the system(3) system
120 call.
121 explain_message_errno_system
123 void explain_message_errno_system(char *message, int message_size, int
124 errnum, const char *command);
125 The explain_message_errno_system function may be used to obtain an
127 explanation of an error returned by the system(3) system call. The
128 least the message will contain is the value of strerror(errnum), but
129 usually it will do much better, and indicate the underlying cause in
130 more detail.
131 This function is intended to be used in a fashion similar to the fol‐
133 lowing example:
134 if (system(command) < 0)
135 {
136 int err = errno;
137 char message[3000];
138 explain_message_errno_system(message, sizeof(message), err, command);
139 fprintf(stderr, "%s\n", message);
140 exit(EXIT_FAILURE);
141 }
142 message The location in which to store the returned message. If a
144 suitable message return buffer is supplied, this function is
145 thread safe.
146 message_size
148 The size in bytes of the location in which to store the
149 returned message.
150 errnum The error value to be decoded, usually obtained from the errno
152 global variable just before this function is called. This is
153 necessary if you need to call any code between the system call
154 to be explained and this function, because many libc functions
155 will alter the value of errno.
156 command The original command, exactly as passed to the system(3) system
158 call.
159
161 system(3)
162 execute a shell command
163 explain_system_or_die(3)
165 execute a shell command and report errors
166
168 libexplain version 1.4
169 Copyright (C) 2008 Peter Miller
170 explain_system(3)