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[/] [openrisc/] [tags/] [gnu-src/] [gdb-7.2/] [gdb-7.2-or32-1.0rc1/] [readline/] [examples/] [excallback.c] - Rev 341
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/* 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 */ #if defined (HAVE_CONFIG_H) #include <config.h> #endif #include <stdio.h> #include <sys/types.h> #ifdef HAVE_UNISTD_H #include <unistd.h> #endif #include <termios.h> /* xxx - should make this more general */ #ifdef READLINE_LIBRARY # include "readline.h" #else # include <readline/readline.h> #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; }