Here Document

Syntax:

command << label
input line 1
…
input line n
label

This allows you to redirect input to a shell script from within the shell script itself.

<< label indicates that label marks the end of the here document
label must appear on a line by itself to end the here document
<< 'label' prevents the shell from doing parameter and command substitution in the here document
<<- label deletes leading tabs (but not spaces) from the here document

Here Document Example
(from page 189 in "Learning the Korn Shell")

pgmname=$1
for user in $(ypcat passwd | cut -f1 -d:)
do
  mail $user <<- EOF
  Dear user,
  A new version of $pgmname has been installed
  in $(whence $pgmname).
  Regards,
  Your friendly sysadmin
EOF
done

原文： http://snap.nlc.dcccd.edu/reference/scarlatos/cis2.50/note6.html

Here Document

Here Document

Here Document Example (from page 189 in "Learning the Korn Shell")

Here Document Example
(from page 189 in "Learning the Korn Shell")