diff --git a/check.r b/check.r
new file mode 100644
index 0000000..b58fe40
--- /dev/null
+++ b/check.r
@@ -0,0 +1,54 @@
+library(httr)
+library(stringr)
+
+u <- str_c(
+  "https://raw.githubusercontent.com/",
+  "briatte/awesome-network-analysis/",
+  "master/README.md"
+)
+
+u <- GET(u) %>%
+  content("text") %>%
+  str_split("\\n") %>% # so as to find [foo]: bar links
+  unlist
+
+# total number of links
+t <- str_count(u, "http") %>%
+  sum
+
+cat(t, "URLs, ")
+
+l <- c(
+  # [foo](bar)
+  str_extract_all(u, "\\(http(.*?)\\)") %>%
+    lapply(str_replace_all, "^\\(|\\)$", "") %>%
+    unlist,
+  # [foo]: bar
+  str_extract_all(u, "^\\[(.*)\\]: (.*)") %>% 
+    unlist %>%
+    str_replace("^\\[(.*)\\]: (.*)", "\\2")
+)
+
+stopifnot(length(l) == t)
+
+l <- unique(l)
+cat(length(l), "unique\n")
+
+for (i in l) {
+  
+  if (!which(l == i) %% 25)
+    cat(length(l) - which(l == i), "left\n")
+  
+  x <- try(GET(i) %>%
+             status_code,
+           silent = TRUE)
+  
+  if (!"try-error" %in% class(x) && x != 200) {
+    cat("\nURL:", i, "\nStatus code:", x, "\n")
+  } else if("try-error" %in% class(x)) {
+    cat("\nURL:", i, "\nFailed to access\n.")
+  } else {
+    cat(".")
+  }
+  
+}