| 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 | |
| 158 | int |
| 159 | change_prompt(void) |
| 160 | { |
| 161 | /* toggle the prompt variable */ |
| 162 | prompt = !prompt; |
| 163 | |
| 164 | /* save away the current contents of the line */ |
| 165 | strcpy(line_buf, rl_line_buffer); |
| 166 | |
| 167 | /* install a new handler which will change the prompt and erase the current line */ |
| 168 | rl_callback_handler_install(get_prompt(), process_line); |
| 169 | |
| 170 | /* insert the old text on the new line */ |
| 171 | rl_insert_text(line_buf); |
| 172 | |
| 173 | /* redraw the current line - this is an undocumented function. It invokes the |
| 174 | * redraw-current-line command. |
| 175 | */ |
| 176 | rl_refresh_line(0, 0); |
| 177 | } |
| 178 | |
| 179 | char * |
| 180 | get_prompt(void) |
| 181 | { |
| 182 | /* The prompts can even be different lengths! */ |
| 183 | sprintf(prompt_buf, "%s", |
| 184 | prompt ? "Hit ctrl-t to toggle prompt> " : "Pretty cool huh?> "); |
| 185 | return prompt_buf; |
| 186 | } |