why doesn't this error message go to the bit bucket?
$ unalias fooee 2>&1 >/dev/null bash: unalias: fooee: not found Why is the error message displayed here? Because of the redirection, I had expected that any error message resulting from the unalias command would go to /dev/null Ronald -- Ronald Fischer (phone +49-89-63676431) mailto:[EMAIL PROTECTED] ___ Bug-bash mailing list Bug-bash@gnu.org http://lists.gnu.org/mailman/listinfo/bug-bash
Re: why doesn't this error message go to the bit bucket?
"Com MN PG P E B Consultant 3" <[EMAIL PROTECTED]> writes: > $ unalias fooee 2>&1 >/dev/null > bash: unalias: fooee: not found > > Why is the error message displayed here? Because you have redirected stderr (fd 2) to the channel connected to stdout (fd 1) before stdout was redirected to a different channel (to /dev/null). > Because of the redirection, I had expected that any error message > resulting from the unalias command would go to /dev/null Read the bash manual, node Redirections: Note that the order of redirections is significant. For example, the command ls > DIRLIST 2>&1 directs both standard output (file descriptor 1) and standard error (file descriptor 2) to the file DIRLIST, while the command ls 2>&1 > DIRLIST directs only the standard output to file DIRLIST, because the standard error was duplicated as standard output before the standard output was redirected to DIRLIST. Andreas. -- Andreas Schwab, SuSE Labs, [EMAIL PROTECTED] SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different." ___ Bug-bash mailing list Bug-bash@gnu.org http://lists.gnu.org/mailman/listinfo/bug-bash
RE: why doesn't this error message go to the bit bucket?
> > $ unalias fooee 2>&1 >/dev/null > > bash: unalias: fooee: not found > > > > Why is the error message displayed here? > > Because you have redirected stderr (fd 2) to the channel connected to > stdout (fd 1) before stdout was redirected to a different channel (to > /dev/null). Of course! Stupid me How could I make such a beginner's mistake! Thank you for pointing this out. Ronald Fischer -- Ronald Fischer (phone +49-89-63676431) mailto:[EMAIL PROTECTED] ___ Bug-bash mailing list Bug-bash@gnu.org http://lists.gnu.org/mailman/listinfo/bug-bash
Re: why doesn't this error message go to the bit bucket?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 According to Com MN PG P E B Consultant 3 on 8/28/2006 2:41 AM: > $ unalias fooee 2>&1 >/dev/null > bash: unalias: fooee: not found > > Why is the error message displayed here? Because of the redirection, > I had expected that any error message resulting from the unalias > command would go to /dev/null Your redirection operators are wrong - you asked bash to copy stderr to the existing stdout, then silence stdout, but since the copy already took place, you are not silencing stderr. So error messages are going to the original stdout, not /dev/null. Try this instead: $ unalias foo >/dev/null 2>&1 Also, if you want to be portable, remember that unalias is a builtin, but that it is optional. The only way to portably silence error messages when your script is designed to run with other shells (such as ash) is to use a subshell to test whether it will work first: $ (unalias foo) >/dev/null 2>&1 && unalias foo - -- Life is short - so eat dessert first! Eric Blake [EMAIL PROTECTED] -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.2.1 (Cygwin) Comment: Public key at home.comcast.net/~ericblake/eblake.gpg Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFE8toZ84KuGfSFAYARAnCHAJ9ZuW980IB+xVTpn5/PEfk/EgUOIACcDR2c zpYhYp0Pf9vmrta/wJynbj8= =+76q -END PGP SIGNATURE- ___ Bug-bash mailing list Bug-bash@gnu.org http://lists.gnu.org/mailman/listinfo/bug-bash
