Perl like select()?

Perl like select()?

[Josh Howard]

Is there any way, in a script, to use a "Perl-like" select() to
associate stdout with a particular file, before the execution of the
rest of the script? For instance: I have a shell script that I want to 
simply put ">log.file" at the top, and then start echo'ing and doing
various output and expect everything to go to log.file, as opposed to
doing something like "./script.sh >> log.file"
In perl, you can open() and select() a file to associate where stdout
is written to. This might be a useful feature in zsh if it doesn't
already exist.


-- 
Josh Howard <jrh@vicor-nb.com>

Re: Perl like select()?

[Zefram]

Josh Howard wrote:
>Is there any way, in a script, to use a "Perl-like" select() to
>associate stdout with a particular file, before the execution of the
>rest of the script?

	exec > file

permanently redirects stdout.  Any redirection can be used this way.

>                    For instance: I have a shell script that I want to 
>simply put ">log.file" at the top, and then start echo'ing and doing
>various output and expect everything to go to log.file,

Interestingly enough, that's the syntax I used for this operation when
designing a new shell from scratch[1].

-zefram

[1] The Elate shell.  It's proprietary and doesn't run on Unix, so don't
ask for it.

Re: Perl like select()?

[Owen M. Astley]

On Wed, 25 Aug 1999, Zefram wrote:

> Josh Howard wrote:
> >Is there any way, in a script, to use a "Perl-like" select() to
> >associate stdout with a particular file, before the execution of the
> >rest of the script?
> 
> 	exec > file
> 
> permanently redirects stdout.  Any redirection can be used this way.

This works in /bin/sh here, but not under zsh (I've tried
zsh-3.0.{0,5,6}), and I've always thought that it was a feature of zsh
that it didn't.

Example...

alpha2----~/tmp% { exec >foo
cursh> echo bar
cursh> }
zsh: command name expected
bar
alpha2----~/tmp% ls -l foo
-rw-r--r--   1 oma1000  colloids       0 Aug 25 17:46 foo

So I guess that there is something odd with my setup.  Does anybody
have any ideas?  Just to start you off, these are the options that I am
setting...

alpha2----~/tmp% grep setop ~/.zshrc
compctl -o setopt unsetopt isset
#unsetopt AUTO_LIST
unsetopt BEEP               # Don't beep ever.
setopt AUTO_LIST            # Auto list ambiguous choices.
#setopt AUTO_MENU            # Use menu completion for 2nd request.
unsetopt MENU_COMPLETE      # Don't use menu completion for 1st request.
setopt ALWAYS_LAST_PROMPT   # List completions after the prompt.
setopt AUTO_NAME_DIRS       # ~dirname instead of absolute names.
setopt EXTENDED_GLOB        # Extended filename globbing.
setopt NO_CLOBBER           # Don't clobber files with >, or create with >>.
setopt LIST_TYPES           # Completions get a trailing id symbol.
setopt INTERACTIVE_COMMENTS # Allow comments in interactive shells.
unsetopt NOTIFY             # Wait before reporting status of background jobs.
unsetopt BG_NICE            # Don't run background jobs at a lower priority.
setopt IGNORE_EOF           # Don't exit on EOF.
setopt MULTIOS              # Glob after redirection operator.
setopt AUTO_PUSHD
setopt PUSHD_IGNORE_DUPS
setopt PUSHD_SILENT PUSHD_TO_HOME PUSHD_MINUS
setopt HIST_IGNORE_DUPS APPEND_HISTORY

Owen

Re: Perl like select()?

[Bart Schaefer]

On Aug 25,  5:16pm, Zefram wrote:
> Subject: Re: Perl like select()?
> Josh Howard wrote:
> >Is there any way, in a script, to use a "Perl-like" select() to
> >simply put ">log.file" at the top, and then start echo'ing and doing
> >various output and expect everything to go to log.file
> 
> Interestingly enough, that's the syntax I used for this operation when
> designing a new shell

NULLCMD=exec

Re: Perl like select()?

[Bart Schaefer]

On Aug 25,  5:48pm, Owen M. Astley wrote:
> Subject: Re: Perl like select()?
> On Wed, 25 Aug 1999, Zefram wrote:
> 
> > 	exec > file
> 
> This works in /bin/sh here, but not under zsh
> 
> alpha2----~/tmp% { exec >foo
> cursh> echo bar
> cursh> }
> zsh: command name expected
> 
> So I guess that there is something odd with my setup.  Does anybody
> have any ideas?

My guess would be that you have exec aliased to something.

Re: Perl like select()?

[Owen M. Astley]

> On Aug 25,  5:48pm, Owen M. Astley wrote:
> > Subject: Re: Perl like select()?
> > On Wed, 25 Aug 1999, Zefram wrote:
> > 
> > > 	exec > file
> > 
> > This works in /bin/sh here, but not under zsh
> 
> My guess would be that you have exec aliased to something.

Ahhhh.  Yes, I wrote a function called exec() so that I didn't
try to execute non-existent commands by mistake!

Thanks
Owen

Re: Perl like select()?

[Josh Howard]

Well, my ignorance is now managable. Thanks.

Zefram <zefram@fysh.org> writes:

> Josh Howard wrote:
> >Is there any way, in a script, to use a "Perl-like" select() to
> >associate stdout with a particular file, before the execution of the
> >rest of the script?
> 
> 	exec > file
> 
> permanently redirects stdout.  Any redirection can be used this way.
> 
> >                    For instance: I have a shell script that I want to 
> >simply put ">log.file" at the top, and then start echo'ing and doing
> >various output and expect everything to go to log.file,
> 
> Interestingly enough, that's the syntax I used for this operation when
> designing a new shell from scratch[1].
> 
> -zefram
> 
> [1] The Elate shell.  It's proprietary and doesn't run on Unix, so don't
> ask for it.
> 

-- 
Josh Howard <jrh@vicor-nb.com>

Re: Perl like select()?

[Nemeth Ervin]

Hi!

>>>>> Zefram  writes:

> Josh Howard wrote:
>> Is there any way, in a script, to use a "Perl-like" select() to
>> associate stdout with a particular file, before the execution of the
>> rest of the script?

> 	exec > file

> permanently redirects stdout.  Any redirection can be used this way.

If you want to keep std{in,out,err}, you can also use a new descriptor.

Example:

# -*- sh -*-
local i file

file=~/.ssh/known_hosts

reply=()

[[ -r $file ]] || return

exec 5< $file

while read -u5 -A i
do
    reply=($reply $i[1])
done

exec 5<&-


-- 
  ____                 ____________________________________________________
 /____| NEMETH, ERVIN |____________________________________________________|
//	< airwin @ inf.bme.hu >		http://www.inf.bme.hu/~airwin
||
||	"Nonsense.  All you have to do is say 'Engage'"
||					-- Patrick Stewart about warp theory

Re: Perl like select()?

[Jay Sekora]

> For instance: I have a shell script that I want to 
> simply put ">log.file" at the top, and then start echo'ing and doing
> various output and expect everything to go to log.file, as opposed to
> doing something like "./script.sh >> log.file"

In the Bourne shell, you use "exec" with redirection and no command, 
thusly:

  #!/bin/zsh
  exec > /tmp/foo
  echo this is a test

And empirically, this works in zsh as well (3.0.5), although the section 
on "exec" in zshmisc(1) doesn't seem to imply that it should.

-j.