four/getch.c


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#include <stdio.h>
#include <string.h>

#define BUFSIZE 101

char buf[BUFSIZE];
int bufp = 0;

/*
 * deliver the next character to be considered
 * reading from the buffer if it contains a character
 * and calling getchar if the buffer is empty
 */
int
getch(void)
{
	return (bufp > 0) ? buf[--bufp] : getchar();
}

/* remember the characters put back on the input */
void
ungetch(int c)
{
	if (bufp >= BUFSIZE) {
		printf("ungetch: too many characters\n");
	} else {
		buf[bufp++] = c;
	}
}

void
ungets(char s[])
{
	int l = strlen(s);
	while (l) {
		ungetch(s[--l]);
	}
}