Annotation of embedaddon/readline/examples/excallback.c, revision 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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