docs: edited lots of libcurl docs for clarity

docs/libcurl/opts/CURLOPT_DEBUGFUNCTION.3

@@ -79,7 +79,103 @@ NULL
 .SH PROTOCOLS
 All
 .SH EXAMPLE
-http://curl.haxx.se/libcurl/c/debug.html
+.nf
+static
+void dump(const char *text,
+          FILE *stream, unsigned char *ptr, size_t size)
+{
+  size_t i;
+  size_t c;
+  unsigned int width=0x10;
+
+  fprintf(stream, "%s, %10.10ld bytes (0x%8.8lx)\n",
+          text, (long)size, (long)size);
+
+  for(i=0; i<size; i+= width) {
+    fprintf(stream, "%4.4lx: ", (long)i);
+
+    /* show hex to the left */
+    for(c = 0; c < width; c++) {
+      if(i+c < size)
+        fprintf(stream, "%02x ", ptr[i+c]);
+      else
+        fputs("   ", stream);
+    }
+
+    /* show data on the right */
+    for(c = 0; (c < width) && (i+c < size); c++)
+      fputc(ptr[i+c]>=0x20) && (ptr[i+c]<0x80)?ptr[i+c]:'.', stream);
+
+    fputc('\n', stream); /* newline */
+  }
+}
+
+static
+int my_trace(CURL *handle, curl_infotype type,
+             char *data, size_t size,
+             void *userp)
+{
+  const char *text;
+  (void)handle; /* prevent compiler warning */
+
+  switch (type) {
+  case CURLINFO_TEXT:
+    fprintf(stderr, "== Info: %s", data);
+  default: /* in case a new one is introduced to shock us */
+    return 0;
+
+  case CURLINFO_HEADER_OUT:
+    text = "=> Send header";
+    break;
+  case CURLINFO_DATA_OUT:
+    text = "=> Send data";
+    break;
+  case CURLINFO_SSL_DATA_OUT:
+    text = "=> Send SSL data";
+    break;
+  case CURLINFO_HEADER_IN:
+    text = "<= Recv header";
+    break;
+  case CURLINFO_DATA_IN:
+    text = "<= Recv data";
+    break;
+  case CURLINFO_SSL_DATA_IN:
+    text = "<= Recv SSL data";
+    break;
+  }
+
+  dump(text, stderr, (unsigned char *)data, size);
+  return 0;
+}
+
+int main(void)
+{
+  CURL *curl;
+  CURLcode res;
+
+  curl = curl_easy_init();
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, my_trace);
+
+    /* the DEBUGFUNCTION has no effect until we enable VERBOSE */
+    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
+
+    /* example.com is redirected, so we tell libcurl to follow redirection */
+    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
+
+    curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/");
+    res = curl_easy_perform(curl);
+    /* Check for errors */
+    if(res != CURLE_OK)
+      fprintf(stderr, "curl_easy_perform() failed: %s\n",
+              curl_easy_strerror(res));
+
+    /* always cleanup */
+    curl_easy_cleanup(curl);
+  }
+  return 0;
+}
+.fi
 .SH AVAILABILITY
 Always
 .SH RETURN VALUE

docs/libcurl/opts/CURLOPT_ERRORBUFFER.3

@@ -48,10 +48,25 @@ NULL
 .SH PROTOCOLS
 All
 .SH EXAMPLE
-TODO
+.nf
+curl = curl_easy_init();
+if(curl) {
+  char error[CURL_ERROR_SIZE]
+
+  curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
+
+  /* provide a buffer to store errors in */
+  curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, error);
+
+  /* Perform the request */
+  curl_easy_perform(curl);
+}
+.fi
 .SH AVAILABILITY
 Always
 .SH RETURN VALUE
 Returns CURLE_OK
 .SH "SEE ALSO"
 .BR CURLOPT_DEBUGFUNCTION "(3), " CURLOPT_VERBOSE "(3), "
+.BR curl_easy_strerror "(3), " curl_multi_strerror "(3), "
+.BR curl_share_strerror "(3) "

docs/libcurl/opts/CURLOPT_PROTOCOLS.3

@@ -88,4 +88,4 @@ Added in 7.19.4
 .SH RETURN VALUE
 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
 .SH "SEE ALSO"
-.BR CURLOPT_REDIR_PROTOCOLS "(3), "
+.BR CURLOPT_REDIR_PROTOCOLS "(3), " CURLOPT_URL "(3), "