ansi_c_pg31_ch01_ex19.c

/*
 * Exercise 1-19.
 * Write a function reverse(s) that reverses the character string s.
 * Use it to write a program that reverses its input a line at a time.
 */


#include <stdio.h>
#define MAXLINE 1000		/* maximum input line length */

int
get_line(char s[], int lim) {
	int             c, i;
	for (i = 0; i < lim - 1 && (c = getchar()) != EOF && c != '\n'; ++i)
		s[i] = c;
	if (c == '\n') {
		s[i] = c;
		++i;
	}
	s[i] = '\0';
	return i;
}
void reverse(char *str) {
	int i, len;
	char c;

	i = 0;

	/* calculate the length of the string */
	while (str[i] != '\0' && str[i] != '\n') {
		++i;
	}

	len = i;
	/* reverse the string */
	for (i = 0; i < len/2; i++) {
		c = str[i];
		str[i] = str[len - 1 - i];
		str[len - 1 - i] = c;
	}
}

int
main()
{
	int   len;
	char   line[MAXLINE];
	/* current line length */
	/* maximum length seen so far */
	while ((len = get_line(line, MAXLINE)) > 0) {
		reverse(line);
		printf("%s",line);
	}
	return (0);
}