1 /* 
2  * 1-19. Write a function reverse(s) that reverses the character string s.
3  * Use it to write a program that reverses its input a line at a time.
4  */
5 
6 /* MAXLINE has been reduced for easier testing */
7 #include <stdio.h>
8 #define MAXLINE 1000
9 
10 int getlin(char line[], int maxline);
11 void copy(char to[], char from[]);
12 int strln(char s[]);
13 void rverse(char s[]);
14 
15 main()
16 {
17 	int len;	/* current line length */
18 	char line[MAXLINE];	/* current input line */
19 	
20 	while ((len = getlin(line, MAXLINE)) > 0) {
21 		rverse(line);
22 		printf("%s\n", line);
23 	}
24 	return 0;
25 }
26 
27 int strln(char s[])
28 {
29 	int i;
30 	for (i=0; s[i] != '\0'; ++i)
31 		;
32 	return i;
33 }
34 
35 void rverse(char s[])
36 {
37 	int i, len;
38 	char c;
39 	len = strln(s);
40 
41 	for (i = 0; i < len/2; ++i) {
42 		c = s[i];
43 		s[i] = s[len-1-i];
44 		s[len-1-i] = c;
45 	}
46 }
47 
48 int getlin(char s[], int lim)
49 {
50 	int c, i;
51 
52 	for (i=0; i<lim-1 && (c=getchar())!=EOF && c!='\n'; ++i)
53 		s[i] = c;
54 	if (c == '\n') {
55 		++i;
56 	}
57 	s[i] = '\0';
58 	return i;
59 }
60 
61 void copy(char to[], char from[])
62 {
63 	int i;
64 	i = 0;
65 	while ((to[i] = from[i]) != '\0')
66 		++i;
67 }