Redirecting output to inline input (here) documents

You can redirect output to inline input (here) documents.

If a command is in the following form:

command << eofstring

and eofstring is any string that does not contain pattern-matching characters, then the shell takes the subsequent lines as the standard input of command until the shell reads a line consisting of only eofstring (possibly preceded by one or more tab characters). The lines between the first eofstring and the second are frequently referred to as an inline input document, or a here document. If a hyphen (-) immediately follows the << redirection characters, the shell strips leading tab characters from each line of the here document before it passes the line to command.

The shell creates a temporary file containing the here document and performs variable and command substitution on the contents before passing the file to the command. It performs pattern matching on file names that are part of command lines in command substitutions. To prohibit all substitutions, quote any character of the eofstring:

command << \eofstring

The here document is especially useful for a small amount of input data that is more conveniently placed in the shell procedure rather than kept in a separate file (such as editor scripts). For example, you could type the following:

cat <<- xyz   
   This message will be shown on the 
   display with leading tabs removed.
   xyz