From bdc39e9353244eb5ee665273b86bc3c5a120c030 Mon Sep 17 00:00:00 2001
From: Zhineng Li <im@zhineng.li>
Date: Wed, 4 Feb 2026 12:00:07 +0800
Subject: ch01-18: remove trailing blanks and tabs from each line of input

---
 ch01/ex18-rtrim.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 ch01/ex18-rtrim.c

(limited to 'ch01/ex18-rtrim.c')

diff --git a/ch01/ex18-rtrim.c b/ch01/ex18-rtrim.c
new file mode 100644
index 0000000..b01d2ef
--- /dev/null
+++ b/ch01/ex18-rtrim.c
@@ -0,0 +1,54 @@
+#include <stdio.h>
+#define MAXLINE 1000	/* maximum input line size */
+
+int getln(char line[], int maxline);
+int rtrim(char line[], int len);
+
+/* remove trailing blanks and tabs from each line of input */
+int main()
+{
+	int len;	/* current line length */
+	char line[MAXLINE];	/* current input line */
+
+	while ((len = getln(line, MAXLINE)) > 0)
+		if ((len = rtrim(line, len)) > 0)
+			printf("%s", line);
+	return 0;
+}
+
+/* getln:  read a line into s, return length */
+int getln(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;
+	}
+	return i;
+}
+
+/* rtrim:  remove trailing blanks and tabs */
+int rtrim(char s[], int len)
+{
+	int nl = 0;
+
+	if (s[len-1] == '\n') {
+		nl = 1;
+		--len;
+	}
+
+	while (len > 0 && (s[len-1] == ' ' || s[len-1] == '\t'))
+		--len;
+
+	if (nl == 1) {
+		s[len] = '\n';
+		++len;
+	}
+
+	s[len] = '\0';
+
+	return len;
+}
-- 
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