The here document <<

Shell Programming and Scripting
1

Hello,

I want to know the use of the here document with the << operator.
Tried to go through some books but the concept was not clear.

Please can any1 expalin me this with a simple example.

Thanks,
Rahul.

2

ftp machine << EOF
cd dirName
put file1
quit
EOF

Above is an example where ftp reads commands till it finds EOF. Inorder for above example to work u have to have .netrc configured ( with out asking for passwd).

3

2 more examples ..

#!/usr/bin/ksh

tr "[a-z]" "[A-Z]" <<EOF
hello world
EOF

cat > file1 <<EOF
abcdefghijklmanopqr
stuv
wxyz
EOF

cat file1

4

Can any1 give me any example for writing interactive programs using the here document.

Thanks,
Rahul.

5

bhargav has already given you three examples of here document usage.

You say you want to write an "interactive" program using a here document? The very nature and purpose of a here document is to take away user interaction and provide automation.

If you have a specific requirement, then please post what it is you're trying to do.

Cheers
ZB

6

Thanks to all of u,

Now i got the concept of the here document.

The idea is that interactive programs can take input from this here document without waiting for user input.

7

hi....i understood why the here block is used...but i fail to understand the exact control flow behind it...i mean how does is work and what is the concept behind it? can u kindly throw some light on it? thanks again