shell中的heredoc使用

shell中的heredoc很有用，对于临时的创建一个较长的字符串，比如脚本中要创建一个脚本等，就可以用这个 参考 Here Documents heredoc中的变量，shell命令都会被执行 下面的脚本创建了一串ftp命令，供ftp命令使用

Filename=`basename $1`           # Strips pathname out of file name.

Server="ibiblio.org"
Directory="/incoming/Linux"
#  These need not be hard-coded into script,
#+ but may instead be changed to command-line argument.

Password="your.e-mail.address"   # Change above to suit.

ftp -n $Server << End-Of-Session
# -n option disables auto-logon
user anonymous "$Password"     
binary
bell                         
cd $Directory
put "$Filename.lsm"
put "$Filename.tar.gz"
bye
End-Of-Session

注意，如果想输出原始字符，即不希望‘$’符号被替换为变量，需要把引导字符用引号引起来，或者添加转义符。

cat <<"SpecialCharTest"

Directory listing would follow
if limit string were not quoted.
`ls -l`

Arithmetic expansion would take place
if limit string were not quoted.
$((5 + 3))

A a single backslash would echo
if limit string were not quoted.
\\

SpecialCharTest