twentieth exercise

1-20.c

@@ -0,0 +1,46 @@
+#include <stdio.h>
+/* program detab
+   replaces tab in the input with the
+   proper number of blank spaces to
+   the next tab stop
+
+   assume a fixed set of tab stops,
+   say, every n columns */
+
+#define MAXLINE 1000
+#define COLPERTAB 8
+
+int ggetline(char line[], int maxline){
+  int character, index;
+  for(index = 0; index < maxline - 1
+       && (character = getchar()) != EOF
+       && character != '\n'; index++){
+    line[index] = character;
+  }
+  line[index] = '\0';
+  return index;
+}
+
+int main(){
+  char line[MAXLINE];
+  int index, length, column, index2;
+  while ((length = ggetline(line, MAXLINE)) > 0){
+    column = index = 0;
+    while(index < length){
+      if (line[index] != '\t'){
+        putchar(line[index]);
+        column++;
+      }
+      if (line[index] == '\t'){
+        index2 = COLPERTAB - (column % COLPERTAB);
+        column += index2;
+        for(; index2 > 0; index2--){
+          putchar(' ');
+        }
+      }
+      index++;
+    }
+    putchar('\n');
+  }
+  return 0;
+}