Re: redirecting standard output and standard error

Skeeve has shown how to get rid of the stderr output from the system call.

The error message is saying that when "system()" invokes a shell to run your "java -version" command, the shell is unable to find an application called "java" in its current PATH. But I don't understand the "UX:" part.

What operating system and shell are you using? This might account for why the redirection didn't work as expected. On my bsd-based darwin OS, the first of the two commands below produces an error message on the console, but the second does not -- meanwhile, a freebsd system behaves differently:

perl -e 'system( "foo > junk" );
# prints:
# sh: line 1: foo: command not found (on darwin)
# foo: not found (on freebsd 6.1)

perl -e 'system( "foo > junk 2>/dev/null" );
# no output on darwin
# still prints "foo: not found" on freebsd
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I'm not sure if that's a difference in how Perl was built on the two machines I happened to be using, or whether it's a matter of how the shells work.

It may also be relevant that the ability to redirect stderr and stdout separately is only available for Bourne-style shells (sh, bash, ksh, zsh); in "c-style" shells ("csh" and any others like it), you can redirect stdout, and you can have stderr included with stdout when redirecting stdout, and that's all you can do ( 2> errlog is not supported, which is a big reason why I never use csh).

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Re^2: redirecting standard output and standard error by Skeeve (Parson) on Sep 04, 2006 at 15:44 UTC
I guess `system("something 2>/dev/null")` should redirect the error output of "something". Not that of the shell calling "something" So I would expect the error to be displayed when "something" isn't available (the error is produced by the shell) and to be suppressed when "something" is available, but produces an error. `s$$([},&%#}/&/]+}%&{});#$&&s&&$^X.($'^"%]=\&(\|?{%` `+`.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e	[reply] [d/l] [select]

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Re^2: redirecting standard output and standard error
by Skeeve (Parson) on Sep 04, 2006 at 15:44 UTC

system("something 2>/dev/null")

s$$([},&%#}/&/]+}%&{})*;#$&&s&&$^X.($'^"%]=\&(|?*{%
+.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e

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