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--- bash:check_if_bash_is_running_in_interactive_mode [2021/02/04 10:38] – created peter
+++ bash:check_if_bash_is_running_in_interactive_mode [2021/02/04 11:08] (current) – [BASH - Check if bash is running in interactive mode] peter
@@ Line 5: / Line 5: @@
 then
   do_interactive_stuff
+fi
+if [ "$-#*i" == "$-" ]; then
+  ...
 fi
 </code>
@@ Line 15: / Line 20: @@
 </WRAP>
+----
+====== Check if standard input is a TTY ======
+<code bash>
+if [ -t 0 ] ; then
+  echo stdin is a terminal
+  .....
+fi
+</code>
+or
+<code bash>
+if [ -t 1 ] ; then
+  echo stdout is a terminal
+fi
+</code>
+<WRAP info>
+**NOTE:**   **-t FD** is True if FD is opened on a terminal.
+Portable between shells.
+</WRAP>
+----
+===== Examples =====
+<code bash>
+bash <<< 'test -t 0 && echo Y || echo X
+</code>
+writes X
+<code bash>
+bash -c 'test -t 0 && echo Y || echo X
+</code>
+writes Y
+<WRAP info>
+**NOTE:**  This also verifies that the standard input is a TTY; although it can be related but it is NOT the same as the shell's interactive mode, which is requested and indicated by shell's "-i" flag.
+</WRAP>
+----