Statement Relationships & I/O Redirection

Statement Relationships

In order of decreasing precedence:

	Operator	Meaning
	( )	Grouping
	>   >!   >&   >&!   >>   >>!   >>&   >>&!   <   <<	I/O Redirection
	|   |&	Piping (stdout only or stdout + stderr) between concurrent operations
	... &	Background thread or process
	&&    ||	Conditional execution: only if first succeeds or only if first fails
	;	Serial execution

I/O Redirection

	Operator	Meaning
	>   >!   >&   >&!	Output to a file ("!" allows an existing file to be overwritten; "&" redirects both stdout and stderr.)
	>>   >>!   >>&   >>&!	Append to a file
	<	In from a file
	<< string	Inline data: the text on the following lines, up to the line containing only the specified string will be fed as stdin to the statement. Unless part of string is escaped or single, double or backquoted, command and variable substitution will be done on the inline text.

The grammar is completely recursive, so statements of arbitrary complexity can be freely nested, conditionally executed, piped or redirected.