From 3cbdab1805a49e3529c3b90932c11208578dd2cc Mon Sep 17 00:00:00 2001
From: Zhineng Li <im@zhineng.li>
Date: Fri, 29 May 2026 09:14:45 +0800
Subject: ch01-20: replaces tabs with proper spaces

---
 ch01/ex20-detab.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 ch01/ex20-detab.c

(limited to 'ch01')

diff --git a/ch01/ex20-detab.c b/ch01/ex20-detab.c
new file mode 100644
index 0000000..78aae5a
--- /dev/null
+++ b/ch01/ex20-detab.c
@@ -0,0 +1,40 @@
+#include <stdio.h>
+
+#define TABSTOP 8  /* number of columns between tab stops */
+
+void putspace(int len);
+
+
+/* replace tabs with proper spaces */
+int main()
+{
+    int c;
+    int col;
+    int nspace;
+
+    col = 0;
+    while ((c = getchar()) != EOF) {
+        if (c == '\t') {
+            nspace = TABSTOP - (col % TABSTOP);
+            col = col + nspace;
+            putspace(nspace);
+        } else if (c == '\n') {
+            col = 0;
+            putchar(c);
+        } else {
+            ++col;
+            putchar(c);
+        }
+    }
+
+    return 0;
+}
+
+/* print len spaces */
+void putspace(int len)
+{
+    int i;
+
+    for (i = 0; i < len; ++i)
+        putchar(' ');
+}
-- 
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