Annotation of embedaddon/readline/examples/excallback.c, revision 1.1.1.1
1.1 misho 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: Copyright (C) 1999 Jeff Solomon
37: */
38:
39: #if defined (HAVE_CONFIG_H)
40: #include <config.h>
41: #endif
42:
43: #include <sys/types.h>
44:
45: #ifdef HAVE_UNISTD_H
46: #include <unistd.h>
47: #endif
48: #include <stdlib.h>
49:
50: #include <stdio.h>
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:
59: #ifndef STDIN_FILENO
60: # define STDIN_FILENO 0
61: #endif
62:
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: }
164:
165: free (line);
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: }
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