add ex1_22, folds

intro/ex1_22_fold.c

@@ -0,0 +1,55 @@
+#include <stdio.h>
+
+#define MAXLINE 1000    /* maximum characters in a line */ 
+#define FOLDLENGTH 20     /* sub line size */ 
+
+int my_getline(char line[], int maxline);
+void fold(char input[], int maxline, int foldlength);
+
+
+int main()
+{
+  int len;                    /* current line length */ 
+  char line[MAXLINE];         /* current input line */
+
+  while ((len = my_getline(line, MAXLINE)) > 0) {
+    fold(line, MAXLINE, FOLDLENGTH);
+  }
+  return 0;
+}
+
+/* my_getline: reads in a line, return the length */
+int my_getline(char line[], int lim)
+{
+  int c, i;
+
+  for (i = 0; i < lim-1 && (c=getchar()) != EOF && c != '\n'; ++i)
+    line[i] = c;
+  if (c == '\n') {
+    line[i] = c;
+    ++i;
+  }
+  line[i] = '\0';
+  return i;
+}
+
+/* fold: split long input lines into 2 or more shorter lines after
+         the last non-blank character that occurs before the nth
+         column of input. */
+void fold(char input[], int lim, int fold_lim)
+{
+  int i, j;
+  char fold_line[lim];
+
+  j  = 0;
+  for (i = 0; i < lim-1 && input[i] != '\0'; ++i, ++j) {
+    if (j > fold_lim-1 && input[i] != ' ' && input[i] != '\t') {
+      fold_line[j] = '\0';
+      j = 0;
+      printf("%s\n", fold_line);
+    }
+    fold_line[j] = input[i];
+  }
+  fold_line[j] = '\0';
+  printf("%s\n", fold_line);
+}