Filtering output from a system() call

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Im using system () to call an external executable from within perl. When the executable launches, it prints some banner junk I dont want displayed on the screen as it fuzzies up the analysis data i output on my own. Is there anyway to prevent output like this from an exe? The exe writes data to a logfile, which is really what Im after, and the extra banner stuff it dumps to the screen is just unwanted.

update (broquaint): title change (was System)

Comment on Filtering output from a system() call

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Re: Filtering output from a system() call by diotalevi (Canon) on Feb 10, 2003 at 06:06 UTC
Filter your executable's output using Filter::Handle. You may want to look at some examples from perlipc for ideas on how to read the output into your perl program. (read the bits on fork, exec and reading from a pipe. "-\|") Seeking Green geeks in Minnesota	[reply]
Re: Filtering output from a system() call by steves (Curate) on Feb 10, 2003 at 06:23 UTC
Since you say "exe" I'm guessing this is Windows. On a UNIX system, the traditonal way to do this would be for the command you execute to be a shell command that redirects standard output to /dev/null or some other bit bucket: `myprogram > /dev/null` [download] There are similar ways to redirect just standard error or both standard output and standard error if it's not that simple: `myprogram 2> /dev/null myprogram > /dev/null 2>&1` [download] You can use IPC::Run to do this sort of thing (different syntax) without invoking a shell.	[reply] [d/l] [select]
Re: Re: Filtering output from a system() call by BrowserUk (Patriarch) on Feb 10, 2003 at 06:50 UTC
The same syntax will work under Win32, the only difference being the name of the bit-bucket. Ie. nul It's worth pointing out that to redirect both handles you can do, `mycommand 1>nul 2>nul` or `mycommand 1>nul 2>&1` or `mycommand 2>nul 1>&2` but that `mycommand 1>&2 2>nul` doesn't work as the first part redirects handle 1 (STDOUT) to wherever handle 2 is currently pointing (which is the same place as STDOUT at that point). The subsequent redirection of handle 2 to the nul device only redirects handle 2 and does not retro-actively re-redirect handle 1. I point this out only because I still get this wrong if I'm doing stuff in a hurry, and I've been doing so for 10+ years. Examine what is said, not who speaks. The 7th Rule of perl club is -- pearl clubs are easily damaged. Use a diamond club instead.	[reply] [d/l] [select]