We no longer have two doc systems, move sphinx_doc_src back to doc_src

doc_src/cmds/echo.rst

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+.. _cmd-echo:
+
+echo - display a line of text
+=============================
+
+Synopsis
+--------
+
+::
+
+    echo [OPTIONS] [STRING]
+
+Description
+-----------
+
+``echo`` displays a string of text.
+
+The following options are available:
+
+- ``-n``, Do not output a newline
+
+- ``-s``, Do not separate arguments with spaces
+
+- ``-E``, Disable interpretation of backslash escapes (default)
+
+- ``-e``, Enable interpretation of backslash escapes
+
+Escape Sequences
+----------------
+
+If ``-e`` is used, the following sequences are recognized:
+
+- ``\`` backslash
+
+- ``\a`` alert (BEL)
+
+- ``\b`` backspace
+
+- ``\c`` produce no further output
+
+- ``\e`` escape
+
+- ``\f`` form feed
+
+- ``\n`` new line
+
+- ``\r`` carriage return
+
+- ``\t`` horizontal tab
+
+- ``\v`` vertical tab
+
+- ``\0NNN`` byte with octal value NNN (1 to 3 digits)
+
+- ``\xHH`` byte with hexadecimal value HH (1 to 2 digits)
+
+Example
+-------
+
+
+
+::
+
+    echo 'Hello World'
+
+Print hello world to stdout
+
+
+
+::
+
+    echo -e 'Top\\nBottom'
+
+Print Top and Bottom on separate lines, using an escape sequence