linux程序设计中一个例题的疑问
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <termios.h>
#include <term.h>
#include <curses.h>
static FILE *output_stream = (FILE *)0;
char *menu[] = {
"a - add new record",
"d - delete record",
"q - quit",
NULL};
int getchoice(char *grreet, char *choices[], FILE *in, FILE *out);
int char_to_terminal(int char_to_write);
int main()
{
char choice = 0;
FILE *input;
FILE *output;
struct termios initial_settings, new_settings;
if(!isatty(fileno(stdout)))
{
fprintf(stderr, "You are not a terminal, OK.\n");
}
input = fopen("/dev/tty", "r");
output = fopen("/dev/tty", "w");
if(!input || !output)
{
fprintf(stderr, "Unable to open /dev/tty\n");
exit(1);
}
tcgetattr(fileno(input), &initial_settings);
new_settings = initial_settings;
new_settings.c_lflag &= ~ICANON;
new_settings.c_lflag &= ~ECHO;
new_settings.c_cc[VMIN] = 1;
new_settings.c_cc[VTIME] = 0;
new_settings.c_lflag &= ~ISIG;
if(tcsetattr(fileno(input), TCSANOW, &new_settings))
fprintf(stderr, "Could not set attributes\n");
do
{
choice = getchoice("Please select an action", menu, input, output);
fprintf(output, "You have chosen: %c\n", choice);
sleep(1);
}while(choice != 'q');
tcsetattr(fileno(input), TCSANOW, &initial_settings);
exit(0);
}
int getchoice(char *greet, char *choices[], FILE *in, FILE *out)
{
int chosen = 0;
char selected;
int screenrow, screencol = 10;
char **option;
char *cursor, *clear;
output_stream = out;
setupterm(NULL, fileno(out), (int *)0);
cursor = tigetstr("cup");
clear = tigetstr("clear");
screenrow = 4;
tputs(clear, 1, char_to_terminal);
tputs(tparm(cursor, screenrow, screencol), 1, char_to_terminal);
fprintf(out, "Choice:%s", greet);
screenrow += 2;
option = choices;
while(*option)
{
tputs(tparm(cursor, screenrow, screencol), 1, char_to_terminal);
fprintf(out, "%s", *option);
screenrow++;
option++;
}
fprintf(out, "\n请输入:");
do
{
fflush(out);
selected = fgetc(in);
option = choices;
while(*option)
{
if(selected == *option[0])
{
chosen = 1;
break;
}
option++;
}
if(!chosen)
{
tputs(tparm(cursor, screenrow, screencol), 1, char_to_terminal);
fprintf(out, "Incorrect choice, select again\n");
}
}while(!chosen);
tputs(clear, 1, char_to_terminal);
return selected;
}
int char_to_terminal(int char_to_write)
{
if (output_stream)
putc(char_to_write, output_stream);
return 0;
}
do
{
choice = getchoice("Please select an action", menu, input, output);
fprintf(output, "You have chosen: %c\n", choice);
sleep(1);
}while(choice != 'q');
