1 Writing Userinfo Modules
2 ------------------------
4 This document describes how to write your own modules for use with the
7 Here are the available functions for modules:
9 void (ui_module_init)(int *chainable);
10 Setup any defaults or anything that needs to be initialized for your
11 module here. The only parameter is a pointer to an integer which
12 should be set to 1 if the module is chainable and 0 if not. Chainable
13 means the previous module was passed the -x or -X option and this
14 module is at the middle or end of the module chain.
16 void (ui_module_exit)(void);
17 Your module should free any resources allocated and close any files
18 here. This is called just before the main program exits.
20 void *(ui_module_help)(void);
21 This displays help on the command line. Put a bunch of printf()'s in
22 here to show available command-line options for your module. Try to
23 keep the help output consistant with other modules (see -h).
25 char *(ui_module_options_init)(char **defaults);
26 This function should return an option string which is compatible with
27 getopt(3) for any options your module may take. The "defaults"
28 argument should be the default options you'd want specified (only
29 options without option arguments are supported) if none are specified
30 for this module on the command line or in the configuration file. If
31 your module takes no options then return NULL; this will bypass any
32 ui_module_options() calls (see below). If you do not want to set any
33 default options, then set "defaults" to NULL.
35 int (ui_module_options)(int argc, char **argv);
36 This function should parse your module command-line options via
37 getopt(3). It takes two arguments which are the argument count and
38 argument list as if passed to the main() function.
40 int (ui_module_exec)(char ***, const struct passwd *, const int, const int,
42 This is the main module function. Each module has this function called
43 in sequence of other modules and not directly after the option
44 parsing. This should be taken into consideration when loading a module
45 more than once. It takes a few arguments:
46 1 - A pointer to an array of character pointers holding strings
47 which will be output in the order they have been added. If
48 this parameter is initialized (not NULL), then chaining has
49 been requested for this module (either -x or -X from the
50 command-line, or '>' or '-' from the configuration file).
52 2 - A password structure for the current username.
54 3 - A character which separates multi-string values. This can be
55 specified on the command line (-m). For example, the password
56 module can output all groups a user belongs to. These groups
57 are separated by a comma (by default) rather than the field
60 4 - Whether the -v option was passed on the command line
61 (verbose). Useful if you want to limit the display unless
64 5 - The strftime() time format. This is either the default or the
65 value of the -t command line option. If you have any values
66 that contain seconds-from-epoch, you should pass this format
67 string to strftime() to maintain output consistency.
69 This function should return an integer 0 on success or 1 on general
70 failure. Note that this affects the program exit status.
72 The output for fields which contain static information should be
73 consistant with the hardcoded values in the main userinfo utility.
74 Type 'ui -h' and look for "Output Key" and assign values for the
75 static fields from this key.
77 Note that the order of output is dependent on the order of module loading and
78 the order of module options.
80 There are three other functions that are built into the userinfo utility which
81 can be used in your module. The first is a function to add a character string
82 to an array of character pointers:
84 void add_string(char ***dest, const char *string);
86 The first argument is the destination buffer and the second is the string to
89 The second function is a time format conversion function. It looks like this:
91 char *stamp(time_t epoch, const char *format);
93 If you have any information arguments that are time strings, you should try
94 and convert them to seconds-since-epoch then run them through the above
95 function. This keeps the time format consistant with other modules (-t command
98 Finally, a safer version of strncat(3) that will always nul-terminate the
99 destination buffer by treating the size N as N-1. Both the dst and src strings
100 must be nul terminated:
102 char *safe_strncat(char *dst, const char *src, size_t n);
104 If you have any questions, feel free to send them to the address below.
106 Ben Kibbey <bjk@luxsci.net>