have zsh invoke a command/script but not exit

have zsh invoke a command/script but not exit

[Tim K. (Gmane)]

Hello,

Is it possible to start zsh and invoke some other command/script but 
upon command completion to return to interactive mode rather than exit 
from zsh? Something like this:

zsh -i -c ls

so that after the ls command is finished I'm left in an interactive shell.

The only way I can think off is to put some hack in my .zshrc where if 
some env variable is set it will run that command at the end of my 
.zshrc file, e.g.

RUN_CMD='ls *.txt' zsh -i

and .zshrc would check for $RUN_CMD and run it at the end.

But even this way I'm struggling with arguments passed to my command, 
how would I run RUN_CMD from .zshrc? Would this be the way to do it:

eval "$RUN_CMD"

Is there a better way to do it?

Thanks for your help.

-- 
Tim

Re: have zsh invoke a command/script but not exit

[Bart Schaefer]

On May 30,  8:51am, Tim K. (Gmane) wrote:
}
} Is it possible to start zsh and invoke some other command/script but 
} upon command completion to return to interactive mode rather than exit 
} from zsh?

After the startup files are finished, zsh reads commands from exactly
one of four places:  The argument of the -c option, the current terminal,
the standard input, or a script file.

A script file is assumed if zsh has arguments but no options specifying
one of the other sources.  The documentation implies that -s forces zsh
to read from stdin, but in fact the -s option only determines whether
any further arguments are taken as the name of a script file; when both
-i and -s appear, -i takes precedence to force input from the terminal.
The -c option overrides both -i and -s, except that the .zshrc file is
read when both -i and -c appear.

The prompt is printed only in interactive mode, and you can't change the
value of that option after startup, so it's impossible to be prompted
after a command has been read from anywhere other than the terminal
(unless you run your own input loop e.g. using "vared").

} The only way I can think off is to put some hack in my .zshrc where if 
} some env variable is set it will run that command at the end of my 
} .zshrc file

How about using $@ instead of an environment variable?

    if [[ $1 == eval ]]
    then
    	"$@"
	set --
    fi

Then you run this as

    zsh -is eval 'ls *.txt'

You could even skip the requirement that "eval" be the first word:

    if (( $# ))
    then
    	eval "$@"
	set --
    fi

However, using "eval" as a keyword there means that you can still use
zsh -is with other argument strings without treating them as commands.

I like this because it lends itself to becoming an alias.

    alias zshi='zsh -is eval '

(The trailing space is for completion purposes.)

Hmm.  Depending on how you expect to use that, you might want to change
the .zshrc part to:

    if [[ $1 == eval ]]
    then
    	"${(q)@}"
	set --
    fi

You can see the difference if you run:

    zshi echo foo \; echo bar
    zshi 'echo foo ; echo bar'

Try each of those both with the (q) and without, and pick the way that
makes the most sense to you.

Re: have zsh invoke a command/script but not exit

[Tim K. (Gmane)]

Thanks for your reply. I have to go learn about the advanced (at least 
to me) things you suggested below.

Tim



Bart Schaefer wrote:

>On May 30,  8:51am, Tim K. (Gmane) wrote:
>}
>} Is it possible to start zsh and invoke some other command/script but 
>} upon command completion to return to interactive mode rather than exit 
>} from zsh?
>
>After the startup files are finished, zsh reads commands from exactly
>one of four places:  The argument of the -c option, the current terminal,
>the standard input, or a script file.
>
>A script file is assumed if zsh has arguments but no options specifying
>one of the other sources.  The documentation implies that -s forces zsh
>to read from stdin, but in fact the -s option only determines whether
>any further arguments are taken as the name of a script file; when both
>-i and -s appear, -i takes precedence to force input from the terminal.
>The -c option overrides both -i and -s, except that the .zshrc file is
>read when both -i and -c appear.
>
>The prompt is printed only in interactive mode, and you can't change the
>value of that option after startup, so it's impossible to be prompted
>after a command has been read from anywhere other than the terminal
>(unless you run your own input loop e.g. using "vared").
>
>} The only way I can think off is to put some hack in my .zshrc where if 
>} some env variable is set it will run that command at the end of my 
>} .zshrc file
>
>How about using $@ instead of an environment variable?
>
>    if [[ $1 == eval ]]
>    then
>    	"$@"
>	set --
>    fi
>
>Then you run this as
>
>    zsh -is eval 'ls *.txt'
>
>You could even skip the requirement that "eval" be the first word:
>
>    if (( $# ))
>    then
>    	eval "$@"
>	set --
>    fi
>
>However, using "eval" as a keyword there means that you can still use
>zsh -is with other argument strings without treating them as commands.
>
>I like this because it lends itself to becoming an alias.
>
>    alias zshi='zsh -is eval '
>
>(The trailing space is for completion purposes.)
>
>Hmm.  Depending on how you expect to use that, you might want to change
>the .zshrc part to:
>
>    if [[ $1 == eval ]]
>    then
>    	"${(q)@}"
>	set --
>    fi
>
>You can see the difference if you run:
>
>    zshi echo foo \; echo bar
>    zshi 'echo foo ; echo bar'
>
>Try each of those both with the (q) and without, and pick the way that
>makes the most sense to you.
>
>  
>