Mercurial > octave-nkf
comparison readline/examples/excallback.c @ 3794:e42e28db4dda
[project @ 2001-02-10 05:14:17 by jwe]
author | jwe |
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date | Sat, 10 Feb 2001 05:15:42 +0000 |
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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 } | |
156 | |
157 free (line); | |
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 } |