it *probably* works

tee.c

@@ -0,0 +1,70 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <string.h>
+
+/*
+  Why is it always the fucking GNU Project causing
+  problems?! For fuck's sake!
+
+  -Kat
+ */
+#ifdef __GLIBC__
+#define __USE_POSIX2
+#endif
+#include <unistd.h>
+
+int main(int argc, char * argv[]) {
+  char c; int start_arg = 1;
+  int append_mode = 0;
+  int file_failed = 0;
+
+  while((c = getopt(argc, argv, "ai")) != -1) {
+    switch(c) {
+      case 'a': append_mode = 1; break;
+      case 'i': signal(SIGINT, SIG_IGN); break;
+    }
+  }
+  
+  while(strcmp("-a", argv[start_arg]) == 0 && 
+        strcmp("-i", argv[start_arg]) == 0 &&
+        strcmp("-ai", argv[start_arg]) == 0 && 
+        strcmp("-ia", argv[start_arg]) == 0) {
+    start_arg++;
+  }
+
+  if(start_arg >= argc) {
+    fprintf(stderr, "%s: no file operands provided\n", argv[0]);
+    return 1;
+  }
+
+  FILE * files[27] = { 0 };
+
+  char * mode = append_mode == 1 ? "a+" : "w+";
+
+  int j = 0;
+  for(int i = start_arg; i < argc && j < 27; i++) {
+    files[j++] = fopen(argv[i], mode);
+    if(files == NULL) {
+      fprintf(stderr, "%s: could not open/create file %s\n", argv[0], argv[i]);
+      return 2;
+    }
+  }
+
+  while((c = getchar()) != EOF) {
+    for(j = 0; files[j] != 0 && j < 27; j++) {
+      if(fputc(c, files[j]) == EOF) {
+        file_failed = 1;
+      }
+    }
+  }
+
+  for(j = 0; files[j] != 0 && j < 27; j++) {
+    if(fclose(files[j]) == EOF) {
+      fprintf(stderr, "%s: failed to close file %s\n", 
+              argv[0], argv[j+start_arg]);
+    }
+  }
+
+  return file_failed == 0 ? 0 : 3;
+}