[CentOS] [OT] bash here documents

Mon Jun 24 14:39:25 UTC 2013
Tony Mountifield <tony at softins.co.uk>

In article <20130624135817.10QZO.129278.root at cdptpa-web19-z02>,
Steve <zephod at cfl.rr.com> wrote:
> Suppose I have this C++ program:
> #include <iostream>
> int main (int argc, char** argv)
> {
>     while (1)
>     {
>         char cmd[80];
>         std::cin.getline(cmd, 80);
>         std::cout << "response to " << cmd << std::endl;
>     }
> }
> compiled by: c++ -o junk junk.cpp
> and I have this bash script:
> #!/bin/bash
> ./junk <<EOF
> blah
> bleh
> \cC
> echo "Something else"
> When I run the script, the program starts and waits for input forever.
> I have 2 questions:
> 1) The "blah" and "bleh" line are not echoed to cout. Why not? Does the here document not send the data to stdin?
> 2) How do I terminate the program? When run interactively, I use <ctrl>-C. 

You should be testing the return value from std::cin.getline() for
end-of-file. You are not testing it for any error. Always test return values.

In your script, the end of the here document will cause your program to see
end-of-file (this is NOT the string "EOF" - that's just the way you denote
the end of the here doc).

And you really ought to find a forum or mailing list where this kind of
question is ON-topic. Flagging the subject OT isn't a magic permission
to post anything you like!

Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org