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1 | /* |
2 | From: Jeff Solomon <jsolomon@stanford.edu> | |
3 | Date: Fri, 9 Apr 1999 10:13:27 -0700 (PDT) | |
4 | To: chet@po.cwru.edu | |
5 | Subject: new readline example | |
6 | Message-ID: <14094.12094.527305.199695@mrclean.Stanford.EDU> | |
7 | ||
8 | Chet, | |
9 | ||
10 | I've been using readline 4.0. Specifically, I've been using the perl | |
11 | version Term::ReadLine::Gnu. It works great. | |
12 | ||
13 | Anyway, I've been playing around the alternate interface and I wanted | |
14 | to contribute a little C program, callback.c, to you that you could | |
15 | use as an example of the alternate interface in the /examples | |
16 | directory of the readline distribution. | |
17 | ||
18 | My example shows how, using the alternate interface, you can | |
19 | interactively change the prompt (which is very nice imo). Also, I | |
20 | point out that you must roll your own terminal setting when using the | |
21 | alternate interface because readline depreps (using your parlance) the | |
22 | terminal while in the user callback. I try to demostrate what I mean | |
23 | with an example. I've included the program below. | |
24 | ||
25 | To compile, I just put the program in the examples directory and made | |
26 | the appropriate changes to the EXECUTABLES and OBJECTS line and added | |
27 | an additional target 'callback'. | |
28 | ||
29 | I compiled on my Sun Solaris2.6 box using Sun's cc. | |
30 | ||
31 | Let me know what you think. | |
32 | ||
33 | Jeff | |
34 | */ | |
35 | ||
36 | #if defined (HAVE_CONFIG_H) | |
37 | #include <config.h> | |
38 | #endif | |
39 | ||
40 | #include <stdio.h> | |
41 | #include <sys/types.h> | |
42 | ||
43 | #ifdef HAVE_UNISTD_H | |
44 | #include <unistd.h> | |
45 | #endif | |
46 | ||
47 | #include <termios.h> /* xxx - should make this more general */ | |
48 | ||
49 | #ifdef READLINE_LIBRARY | |
50 | # include "readline.h" | |
51 | #else | |
52 | # include <readline/readline.h> | |
53 | #endif | |
54 | ||
55 | /* This little examples demonstrates the alternate interface to using readline. | |
56 | * In the alternate interface, the user maintains control over program flow and | |
57 | * only calls readline when STDIN is readable. Using the alternate interface, | |
58 | * you can do anything else while still using readline (like talking to a | |
59 | * network or another program) without blocking. | |
60 | * | |
61 | * Specifically, this program highlights two importants features of the | |
62 | * alternate interface. The first is the ability to interactively change the | |
63 | * prompt, which can't be done using the regular interface since rl_prompt is | |
64 | * read-only. | |
65 | * | |
66 | * The second feature really highlights a subtle point when using the alternate | |
67 | * interface. That is, readline will not alter the terminal when inside your | |
68 | * callback handler. So let's so, your callback executes a user command that | |
69 | * takes a non-trivial amount of time to complete (seconds). While your | |
70 | * executing the command, the user continues to type keystrokes and expects them | |
71 | * to be re-echoed on the new prompt when it returns. Unfortunately, the default | |
72 | * terminal configuration doesn't do this. After the prompt returns, the user | |
73 | * must hit one additional keystroke and then will see all of his previous | |
74 | * keystrokes. To illustrate this, compile and run this program. Type "sleep" at | |
75 | * the prompt and then type "bar" before the prompt returns (you have 3 | |
76 | * seconds). Notice how "bar" is re-echoed on the prompt after the prompt | |
77 | * returns? This is what you expect to happen. Now comment out the 4 lines below | |
78 | * the line that says COMMENT LINE BELOW. Recompile and rerun the program and do | |
79 | * the same thing. When the prompt returns, you should not see "bar". Now type | |
80 | * "f", see how "barf" magically appears? This behavior is un-expected and not | |
81 | * desired. | |
82 | */ | |
83 | ||
84 | void process_line(char *line); | |
85 | int change_prompt(void); | |
86 | char *get_prompt(void); | |
87 | ||
88 | int prompt = 1; | |
89 | char prompt_buf[40], line_buf[256]; | |
90 | tcflag_t old_lflag; | |
91 | cc_t old_vtime; | |
92 | struct termios term; | |
93 | ||
94 | int | |
95 | main() | |
96 | { | |
97 | fd_set fds; | |
98 | ||
99 | /* Adjust the terminal slightly before the handler is installed. Disable | |
100 | * canonical mode processing and set the input character time flag to be | |
101 | * non-blocking. | |
102 | */ | |
103 | if( tcgetattr(STDIN_FILENO, &term) < 0 ) { | |
104 | perror("tcgetattr"); | |
105 | exit(1); | |
106 | } | |
107 | old_lflag = term.c_lflag; | |
108 | old_vtime = term.c_cc[VTIME]; | |
109 | term.c_lflag &= ~ICANON; | |
110 | term.c_cc[VTIME] = 1; | |
111 | /* COMMENT LINE BELOW - see above */ | |
112 | if( tcsetattr(STDIN_FILENO, TCSANOW, &term) < 0 ) { | |
113 | perror("tcsetattr"); | |
114 | exit(1); | |
115 | } | |
116 | ||
117 | rl_add_defun("change-prompt", change_prompt, CTRL('t')); | |
118 | rl_callback_handler_install(get_prompt(), process_line); | |
119 | ||
120 | while(1) { | |
121 | FD_ZERO(&fds); | |
122 | FD_SET(fileno(stdin), &fds); | |
123 | ||
124 | if( select(FD_SETSIZE, &fds, NULL, NULL, NULL) < 0) { | |
125 | perror("select"); | |
126 | exit(1); | |
127 | } | |
128 | ||
129 | if( FD_ISSET(fileno(stdin), &fds) ) { | |
130 | rl_callback_read_char(); | |
131 | } | |
132 | } | |
133 | } | |
134 | ||
135 | void | |
136 | process_line(char *line) | |
137 | { | |
138 | if( line == NULL ) { | |
139 | fprintf(stderr, "\n", line); | |
140 | ||
141 | /* reset the old terminal setting before exiting */ | |
142 | term.c_lflag = old_lflag; | |
143 | term.c_cc[VTIME] = old_vtime; | |
144 | if( tcsetattr(STDIN_FILENO, TCSANOW, &term) < 0 ) { | |
145 | perror("tcsetattr"); | |
146 | exit(1); | |
147 | } | |
148 | exit(0); | |
149 | } | |
150 | ||
151 | if( strcmp(line, "sleep") == 0 ) { | |
152 | sleep(3); | |
153 | } else { | |
154 | fprintf(stderr, "|%s|\n", line); | |
155 | } | |
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156 | |
157 | free (line); | |
f9267e15 EZ |
158 | } |
159 | ||
160 | int | |
161 | change_prompt(void) | |
162 | { | |
163 | /* toggle the prompt variable */ | |
164 | prompt = !prompt; | |
165 | ||
166 | /* save away the current contents of the line */ | |
167 | strcpy(line_buf, rl_line_buffer); | |
168 | ||
169 | /* install a new handler which will change the prompt and erase the current line */ | |
170 | rl_callback_handler_install(get_prompt(), process_line); | |
171 | ||
172 | /* insert the old text on the new line */ | |
173 | rl_insert_text(line_buf); | |
174 | ||
175 | /* redraw the current line - this is an undocumented function. It invokes the | |
176 | * redraw-current-line command. | |
177 | */ | |
178 | rl_refresh_line(0, 0); | |
179 | } | |
180 | ||
181 | char * | |
182 | get_prompt(void) | |
183 | { | |
184 | /* The prompts can even be different lengths! */ | |
185 | sprintf(prompt_buf, "%s", | |
186 | prompt ? "Hit ctrl-t to toggle prompt> " : "Pretty cool huh?> "); | |
187 | return prompt_buf; | |
188 | } |