linux development:detecting output type

Finished bash section. Started writing section explaining how it works
using C.

1 files changed, 61 insertions, 0 deletions

diff --git a/src/linux_development:detecting_output_type.ascii b/src/linux_development:detecting_output_type.ascii
index 792ee3d..235bcae 100644
--- a/src/linux_development:detecting_output_type.ascii
+++ b/src/linux_development:detecting_output_type.ascii
@@ -68,10 +68,71 @@ ____
 
 Let's give this a try.
 
+.test.sh
+----
+#!/usr/bin/env bash
+
+if [[ -t 1 ]]; then
+  echo -e "\e[32mYay! Colored text is cool!\e[0m"
+else
+  echo -e "Boo! Plain text is lame."
+fi
+----
+
+
+If we execute this with './test.sh', we'll see the green colored text "Yay!
+Colored text is cool!".
 
+If we then execute this with './test.sh | less', we'll see the plain text "Boo,
+Plain text is lame." This also outputs plain text if you redirect the output
+using './test.sh > test.out'.
 
 
 
+What -t Really Does
+-------------------
+
+When I saw this functionality in bash, I immediately wanted to know how it
+worked. Sure, I'd read the documentation, but there's no understanding like the
+understanding that comes from writing it in C yourself.
+
+
+----
+#include <stdio.h>
+#include <sys/stat.h>
+
+/**
+ * Detects if the specified file descriptor is a character device, or something
+ * else.
+ * Useful for determiniing if colored output is supported.
+ * 
+ * @param FILE* fd File descriptor to check
+ *
+ * @return int FD is char dev (1) or not (0)
+ */
+int ischardev(FILE* fd) {
+  struct stat d;
+  // stat the file descriptor
+  fstat(fileno(stdout), &d);
+
+  // Check st_mode (see "man 2 stat" for more information about this)
+  if(S_ISCHR(d.st_mode))
+    return 1;
+
+  return 0;
+}
+
+int main(int argc, char* argv[]) {
+  if(ischardev(stdout)) {
+    printf("Character dev. Colors supported\n");
+  } else {
+    printf("Something else. Colors not supported\n");
+  }
+
+  return 0;
+}
+----
+
 
 :revdate: June 29, 2016
 [role="datelastedit"]