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perl... how to tell if a piped command is still running?

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Old 08-17-2005
perl... how to tell if a piped command is still running?
I'm using the fabulous perl. I need a way to tell when a piped call to "open" has completed. Can I do this with a command like <ShellPipe> ??


Reason behind this:

I'm trying to write a backup script in perl! This script will download a certain file from my web server, to my computer.

Now, this perl script calls wget something like this:

open( ShellPipe, "wget http://url.com" );

Is there some way to get wget to delete the file if the file download got interupted? Otherwise I'll have a partially downloaded backup!

My script is smart enough, that it will try again if the file doesn't exist, you see. But what if the download got interupted? Then a file will exist, and I'll have a bad backup.

I know it's unlikely to get interupted, but I like to take care and be very sure of these things Smilie

Also, my webserver does not tell me the size of the file to be downloaded. It tells you when there is no more data, though.

So for this reason, I just need to tell when the pipe has been completed.
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IDLE(1) 						      General Commands Manual							   IDLE(1)

NAME

       IDLE - An Integrated DeveLopment Environment for Python

SYNTAX

       idle [ -dins ] [ -t title ] [ file ...]

       idle [ -dins ] [ -t title ] ( -c cmd | -r file ) [ arg ...]

       idle [ -dins ] [ -t title ] - [ arg ...]

DESCRIPTION

       This  manual page documents briefly the idle command.  This manual page was written for Debian because the original program does not have a
       manual page.  For more information, refer to IDLE's help menu.

       IDLE is an Integrated DeveLopment Environment for Python. IDLE is based on Tkinter, Python's bindings to the Tk widget  set.  Features  are
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OPTIONS

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       The following options imply -i and will open a shell:

       -c cmd Run the command in a shell, or

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       -d     Enable the debugger.

       -s     Run $IDLESTARTUP or $PYTHONSTARTUP before anything else.

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       A default edit window will be bypassed when -c, -r, or - are used.

       [arg]* and [file]* are passed to the command (-c) or script (-r) in sys.argv[1:].

EXAMPLES

       idle   Open an edit window or shell depending on IDLE's configuration.

       idle foo.py foobar.py
	      Edit the files, also open a shell if configured to start with shell.

       idle -est "Baz" foo.py
	      Run $IDLESTARTUP or $PYTHONSTARTUP, edit foo.py, and open a shell window with the title "Baz".

       idle -c "import sys; print sys.argv" "foo"
	      Open a shell window and run the command, passing "-c" in sys.argv[0] and "foo" in sys.argv[1].

       idle -d -s -r foo.py "Hello World"
	      Open a shell window, run a startup script, enable the debugger, and run foo.py, passing "foo.py" in sys.argv[0] and "Hello World" in
	      sys.argv[1].

       echo "import sys; print sys.argv" | idle - "foobar"
	      Open a shell window, run the script piped in, passing '' in sys.argv[0] and "foobar" in sys.argv[1].

SEE ALSO

       python(1).

AUTHORS

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								 21 September 2004							   IDLE(1)