On Wed, Jul 01, 2009 at 10:50:52AM +0200, Sven Joachim wrote:
> On 2009-07-01 10:14 +0200, Todd A. Jacobs wrote:
>
> > I noticed that a bash script of mine was causing permission errors under
> > cron, so I had to change it like so:
> >
> > --- boxmail.sh 2009/06/30 09:01:46 1.10
> > +++ boxmail.sh 2009/07/01 08:01:51
> > @@ -167,7 +167,7 @@
> >
> > # Echo message to standard error.
> > function stderr {
> > - echo "$*" > /dev/stderr
> > + echo "$*" >&2
> > }
> >
> > # Display warnings on standard error.
> >
> > I did a little minor testing with cron, and >&2 works while /dev/stderr
> > doesn't. Now, I know that "/dev/stderr" is a bashism,
>
> Actually, it might be not. On my system, /dev/stderr exists and is a
> symlink to /proc/self/fd/2, i.e. the standard error channel of the
> current process. Thus it works fine with dash.
Right. On linux:
$ ls -l /dev/stderr
lrwxrwxrwx 1 root root 15 2009-06-10 23:35 /dev/stderr -> /proc/self/fd/2
On BSDs and Solaris /dev/stderr is a special device (like /dev/null and
/dev/zero). Though I'm not really sure it is guaranteed by POSIX.
>
> > but since cron is
> > executing boxmail.sh (with an explicit bash shebang) rather than
> > executing the code directly, why would the bashism come back with:
> >
> > From: Cron Daemon
> > To: nospam
> > Subject: Cron <nospam> $HOME/bin/boxmail.sh
> > Date: Wed, 1 Jul 2009 00:00:02 -0700 (PDT)
> >
> > /home/nospam/bin/boxmail.sh: line 170: /dev/stderr: Permission denied
ls -l /dev/stderr
> >
> > The bash manual doesn't say anything about a requirement that the shell
> > be interactive to use /dev/stderr, so why is this happening?
A redirection to &2 is cleaner, anyway. Any reason you have not to use
it?
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