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Full Discussion: Getting value of variable set in subprocess script
Top Forums Shell Programming and Scripting Getting value of variable set in subprocess script Post 80594 by hadarot on Wednesday 10th of August 2005 02:29:42 AM
Old 08-10-2005
Getting value of variable set in subprocess script
I am writing a shell script that executes another script by fetching it over the network and piping its contents into sh (ftp -o - $script | sh; or wget -O - |sh). Since this bypasses putting the script on the filesystem, this means I can't source the script directly (using . ), but rather it gets executed in a subprocess.
So here is my problem: When it comes to Unix processes, information can usually flow only from parent to child (when the parent establishes the child's environment at invocation). But is there a way that the calling script can get a value of a variable that is set in the called script? Could using co-processes solve this, with like read -p?
I know I can fetch the script unto my hard drive, and then source it. Or I can pipe the contents of the script from the network, and save the data I need to a temporary file, and then my main program can get the data from that file. But is there a way to bypass the filesystem alltogether?
And an importnat point: the called script does a lot of stuff on its own. I don't want all of its standard output to come back as input to the calling script, but only the value of a particular variable.
Last edited by hadarot; 08-12-2005 at 05:18 AM..
 

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LEARN ABOUT MOJAVE

tcl_allowexceptions

Tcl_AllowExceptions(3)					      Tcl Library Procedures					    Tcl_AllowExceptions(3)

__________________________________________________________________________________________________________________________________________________

NAME

       Tcl_AllowExceptions - allow all exceptions in next script evaluation

SYNOPSIS

       #include <tcl.h>

       Tcl_AllowExceptions(interp)

ARGUMENTS

       Tcl_Interp *interp (in)		Interpreter in which script will be evaluated.
_________________________________________________________________

DESCRIPTION

       If  a  script is evaluated at top-level (i.e. no other scripts are pending evaluation when the script is invoked), and if the script termi-
       nates with a completion code other than TCL_OK, TCL_ERROR or TCL_RETURN, then Tcl normally converts this into a TCL_ERROR  return  with	an
       appropriate  message.  The particular script evaluation procedures of Tcl that act in the manner are Tcl_EvalObjEx, Tcl_EvalObjv, Tcl_Eval,
       Tcl_EvalEx, Tcl_GlobalEval, Tcl_GlobalEvalObj, Tcl_VarEval and Tcl_VarEvalVA.

       However, if Tcl_AllowExceptions is invoked immediately before calling one of those a procedures, then arbitrary completion codes  are  per-
       mitted from the script, and they are returned without modification.  This is useful in cases where the caller can deal with exceptions such
       as TCL_BREAK or TCL_CONTINUE in a meaningful way.

KEYWORDS

       continue, break, exception, interpreter

Tcl									7.4						    Tcl_AllowExceptions(3)
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