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Diffstat (limited to 'examples/excallback.c')
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diff --git a/examples/excallback.c b/examples/excallback.c new file mode 100644 index 0000000..4206acf --- /dev/null +++ b/examples/excallback.c @@ -0,0 +1,196 @@ +/* +From: Jeff Solomon <jsolomon@stanford.edu> +Date: Fri, 9 Apr 1999 10:13:27 -0700 (PDT) +To: chet@po.cwru.edu +Subject: new readline example +Message-ID: <14094.12094.527305.199695@mrclean.Stanford.EDU> + +Chet, + +I've been using readline 4.0. Specifically, I've been using the perl +version Term::ReadLine::Gnu. It works great. + +Anyway, I've been playing around the alternate interface and I wanted +to contribute a little C program, callback.c, to you that you could +use as an example of the alternate interface in the /examples +directory of the readline distribution. + +My example shows how, using the alternate interface, you can +interactively change the prompt (which is very nice imo). Also, I +point out that you must roll your own terminal setting when using the +alternate interface because readline depreps (using your parlance) the +terminal while in the user callback. I try to demostrate what I mean +with an example. I've included the program below. + +To compile, I just put the program in the examples directory and made +the appropriate changes to the EXECUTABLES and OBJECTS line and added +an additional target 'callback'. + +I compiled on my Sun Solaris2.6 box using Sun's cc. + +Let me know what you think. + +Jeff +*/ +/* +Copyright (C) 1999 Jeff Solomon +*/ + +#if defined (HAVE_CONFIG_H) +#include <config.h> +#endif + +#include <sys/types.h> + +#ifdef HAVE_UNISTD_H +#include <unistd.h> +#endif +#include <stdlib.h> + +#include <stdio.h> +#include <termios.h> /* xxx - should make this more general */ + +#ifdef READLINE_LIBRARY +# include "readline.h" +#else +# include <readline/readline.h> +#endif + +#ifndef STDIN_FILENO +# define STDIN_FILENO 0 +#endif + +/* This little examples demonstrates the alternate interface to using readline. + * In the alternate interface, the user maintains control over program flow and + * only calls readline when STDIN is readable. Using the alternate interface, + * you can do anything else while still using readline (like talking to a + * network or another program) without blocking. + * + * Specifically, this program highlights two importants features of the + * alternate interface. The first is the ability to interactively change the + * prompt, which can't be done using the regular interface since rl_prompt is + * read-only. + * + * The second feature really highlights a subtle point when using the alternate + * interface. That is, readline will not alter the terminal when inside your + * callback handler. So let's so, your callback executes a user command that + * takes a non-trivial amount of time to complete (seconds). While your + * executing the command, the user continues to type keystrokes and expects them + * to be re-echoed on the new prompt when it returns. Unfortunately, the default + * terminal configuration doesn't do this. After the prompt returns, the user + * must hit one additional keystroke and then will see all of his previous + * keystrokes. To illustrate this, compile and run this program. Type "sleep" at + * the prompt and then type "bar" before the prompt returns (you have 3 + * seconds). Notice how "bar" is re-echoed on the prompt after the prompt + * returns? This is what you expect to happen. Now comment out the 4 lines below + * the line that says COMMENT LINE BELOW. Recompile and rerun the program and do + * the same thing. When the prompt returns, you should not see "bar". Now type + * "f", see how "barf" magically appears? This behavior is un-expected and not + * desired. + */ + +void process_line(char *line); +int change_prompt(void); +char *get_prompt(void); + +int prompt = 1; +char prompt_buf[40], line_buf[256]; +tcflag_t old_lflag; +cc_t old_vtime; +struct termios term; + +int +main() +{ + fd_set fds; + + /* Adjust the terminal slightly before the handler is installed. Disable + * canonical mode processing and set the input character time flag to be + * non-blocking. + */ + if( tcgetattr(STDIN_FILENO, &term) < 0 ) { + perror("tcgetattr"); + exit(1); + } + old_lflag = term.c_lflag; + old_vtime = term.c_cc[VTIME]; + term.c_lflag &= ~ICANON; + term.c_cc[VTIME] = 1; + /* COMMENT LINE BELOW - see above */ + if( tcsetattr(STDIN_FILENO, TCSANOW, &term) < 0 ) { + perror("tcsetattr"); + exit(1); + } + + rl_add_defun("change-prompt", change_prompt, CTRL('t')); + rl_callback_handler_install(get_prompt(), process_line); + + while(1) { + FD_ZERO(&fds); + FD_SET(fileno(stdin), &fds); + + if( select(FD_SETSIZE, &fds, NULL, NULL, NULL) < 0) { + perror("select"); + exit(1); + } + + if( FD_ISSET(fileno(stdin), &fds) ) { + rl_callback_read_char(); + } + } +} + +void +process_line(char *line) +{ + if( line == NULL ) { + fprintf(stderr, "\n", line); + + /* reset the old terminal setting before exiting */ + term.c_lflag = old_lflag; + term.c_cc[VTIME] = old_vtime; + if( tcsetattr(STDIN_FILENO, TCSANOW, &term) < 0 ) { + perror("tcsetattr"); + exit(1); + } + exit(0); + } + + if( strcmp(line, "sleep") == 0 ) { + sleep(3); + } else { + fprintf(stderr, "|%s|\n", line); + } + + free (line); +} + +int +change_prompt(void) +{ + /* toggle the prompt variable */ + prompt = !prompt; + + /* save away the current contents of the line */ + strcpy(line_buf, rl_line_buffer); + + /* install a new handler which will change the prompt and erase the current line */ + rl_callback_handler_install(get_prompt(), process_line); + + /* insert the old text on the new line */ + rl_insert_text(line_buf); + + /* redraw the current line - this is an undocumented function. It invokes the + * redraw-current-line command. + */ + rl_refresh_line(0, 0); +} + +char * +get_prompt(void) +{ + /* The prompts can even be different lengths! */ + sprintf(prompt_buf, "%s", + prompt ? "Hit ctrl-t to toggle prompt> " : "Pretty cool huh?> "); + return prompt_buf; +} |