1 files changed, 59 insertions, 0 deletions

diff --git a/1/21.c b/1/21.c
new file mode 100644
index 0000000..8648ee2
--- /dev/null
+++ b/1/21.c
@@ -0,0 +1,59 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAXLEN 1000
+
+void getstr(char s[]);
+void entab(char to[], char from[], int n);
+
+/* replaces specified number of blanks with a tabstop */
+int main(int argc, char *argv[]) {
+  int tabw;
+  char s[MAXLEN], tabbed[MAXLEN];
+
+  tabw = atoi(argv[1]);
+
+  printf("Enter text to entab and press ctrl+d\n");
+
+  getstr(s);
+  entab(tabbed, s, tabw);
+  printf("\nTab width: %d\n", tabw);
+  printf("%s\n", tabbed);
+
+  return 0;
+}
+
+void getstr(char s[]) {
+  int i, c;
+
+  for (i = 0; i < MAXLEN - 1 && (c = getchar()) != EOF; i++)
+    s[i] = c;
+  s[i] = '\0';
+}
+
+void entab(char to[], char from[], int n) {
+  int i, j, k, op;
+  char c;
+
+  for (i = 0, j = 0; j < MAXLEN - 1 && (c = from[j]) != '\0'; i++) {
+    if (c == ' ') {
+      op = j + n < MAXLEN - 1;
+      for (k = j + 1; op && k < j + n - 1; k++) {
+        if (from[k] != ' ') {
+          op = 0;
+        }
+      }
+
+      if (op) {
+        to[i] = '\t';
+        j += n;
+        continue;
+      }
+    }
+
+    to[i] = c;
+    j++;
+  }
+
+  to[i] = '\0';
+}
\ No newline at end of file