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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 | */ | |
cc88a640 JK |
35 | /* |
36 | Copyright (C) 1999 Jeff Solomon | |
37 | */ | |
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38 | |
39 | #if defined (HAVE_CONFIG_H) | |
40 | #include <config.h> | |
41 | #endif | |
42 | ||
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43 | #include <sys/types.h> |
44 | ||
45 | #ifdef HAVE_UNISTD_H | |
46 | #include <unistd.h> | |
47 | #endif | |
775e241e | 48 | #include <stdlib.h> |
f9267e15 | 49 | |
775e241e | 50 | #include <stdio.h> |
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51 | #include <termios.h> /* xxx - should make this more general */ |
52 | ||
53 | #ifdef READLINE_LIBRARY | |
54 | # include "readline.h" | |
55 | #else | |
56 | # include <readline/readline.h> | |
57 | #endif | |
58 | ||
775e241e TT |
59 | #ifndef STDIN_FILENO |
60 | # define STDIN_FILENO 0 | |
61 | #endif | |
62 | ||
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63 | /* This little examples demonstrates the alternate interface to using readline. |
64 | * In the alternate interface, the user maintains control over program flow and | |
65 | * only calls readline when STDIN is readable. Using the alternate interface, | |
66 | * you can do anything else while still using readline (like talking to a | |
67 | * network or another program) without blocking. | |
68 | * | |
69 | * Specifically, this program highlights two importants features of the | |
70 | * alternate interface. The first is the ability to interactively change the | |
71 | * prompt, which can't be done using the regular interface since rl_prompt is | |
72 | * read-only. | |
73 | * | |
74 | * The second feature really highlights a subtle point when using the alternate | |
75 | * interface. That is, readline will not alter the terminal when inside your | |
76 | * callback handler. So let's so, your callback executes a user command that | |
77 | * takes a non-trivial amount of time to complete (seconds). While your | |
78 | * executing the command, the user continues to type keystrokes and expects them | |
79 | * to be re-echoed on the new prompt when it returns. Unfortunately, the default | |
80 | * terminal configuration doesn't do this. After the prompt returns, the user | |
81 | * must hit one additional keystroke and then will see all of his previous | |
82 | * keystrokes. To illustrate this, compile and run this program. Type "sleep" at | |
83 | * the prompt and then type "bar" before the prompt returns (you have 3 | |
84 | * seconds). Notice how "bar" is re-echoed on the prompt after the prompt | |
85 | * returns? This is what you expect to happen. Now comment out the 4 lines below | |
86 | * the line that says COMMENT LINE BELOW. Recompile and rerun the program and do | |
87 | * the same thing. When the prompt returns, you should not see "bar". Now type | |
88 | * "f", see how "barf" magically appears? This behavior is un-expected and not | |
89 | * desired. | |
90 | */ | |
91 | ||
92 | void process_line(char *line); | |
93 | int change_prompt(void); | |
94 | char *get_prompt(void); | |
95 | ||
96 | int prompt = 1; | |
97 | char prompt_buf[40], line_buf[256]; | |
98 | tcflag_t old_lflag; | |
99 | cc_t old_vtime; | |
100 | struct termios term; | |
101 | ||
102 | int | |
103 | main() | |
104 | { | |
105 | fd_set fds; | |
106 | ||
107 | /* Adjust the terminal slightly before the handler is installed. Disable | |
108 | * canonical mode processing and set the input character time flag to be | |
109 | * non-blocking. | |
110 | */ | |
111 | if( tcgetattr(STDIN_FILENO, &term) < 0 ) { | |
112 | perror("tcgetattr"); | |
113 | exit(1); | |
114 | } | |
115 | old_lflag = term.c_lflag; | |
116 | old_vtime = term.c_cc[VTIME]; | |
117 | term.c_lflag &= ~ICANON; | |
118 | term.c_cc[VTIME] = 1; | |
119 | /* COMMENT LINE BELOW - see above */ | |
120 | if( tcsetattr(STDIN_FILENO, TCSANOW, &term) < 0 ) { | |
121 | perror("tcsetattr"); | |
122 | exit(1); | |
123 | } | |
124 | ||
125 | rl_add_defun("change-prompt", change_prompt, CTRL('t')); | |
126 | rl_callback_handler_install(get_prompt(), process_line); | |
127 | ||
128 | while(1) { | |
129 | FD_ZERO(&fds); | |
130 | FD_SET(fileno(stdin), &fds); | |
131 | ||
132 | if( select(FD_SETSIZE, &fds, NULL, NULL, NULL) < 0) { | |
133 | perror("select"); | |
134 | exit(1); | |
135 | } | |
136 | ||
137 | if( FD_ISSET(fileno(stdin), &fds) ) { | |
138 | rl_callback_read_char(); | |
139 | } | |
140 | } | |
141 | } | |
142 | ||
143 | void | |
144 | process_line(char *line) | |
145 | { | |
146 | if( line == NULL ) { | |
147 | fprintf(stderr, "\n", line); | |
148 | ||
149 | /* reset the old terminal setting before exiting */ | |
150 | term.c_lflag = old_lflag; | |
151 | term.c_cc[VTIME] = old_vtime; | |
152 | if( tcsetattr(STDIN_FILENO, TCSANOW, &term) < 0 ) { | |
153 | perror("tcsetattr"); | |
154 | exit(1); | |
155 | } | |
156 | exit(0); | |
157 | } | |
158 | ||
159 | if( strcmp(line, "sleep") == 0 ) { | |
160 | sleep(3); | |
161 | } else { | |
162 | fprintf(stderr, "|%s|\n", line); | |
163 | } | |
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164 | |
165 | free (line); | |
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166 | } |
167 | ||
168 | int | |
169 | change_prompt(void) | |
170 | { | |
171 | /* toggle the prompt variable */ | |
172 | prompt = !prompt; | |
173 | ||
174 | /* save away the current contents of the line */ | |
175 | strcpy(line_buf, rl_line_buffer); | |
176 | ||
177 | /* install a new handler which will change the prompt and erase the current line */ | |
178 | rl_callback_handler_install(get_prompt(), process_line); | |
179 | ||
180 | /* insert the old text on the new line */ | |
181 | rl_insert_text(line_buf); | |
182 | ||
183 | /* redraw the current line - this is an undocumented function. It invokes the | |
184 | * redraw-current-line command. | |
185 | */ | |
186 | rl_refresh_line(0, 0); | |
187 | } | |
188 | ||
189 | char * | |
190 | get_prompt(void) | |
191 | { | |
192 | /* The prompts can even be different lengths! */ | |
193 | sprintf(prompt_buf, "%s", | |
194 | prompt ? "Hit ctrl-t to toggle prompt> " : "Pretty cool huh?> "); | |
195 | return prompt_buf; | |
196 | } |