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Full Discussion: SSH sessions from bash script
Top Forums Shell Programming and Scripting SSH sessions from bash script Post 302307130 by qneill on Tuesday 14th of April 2009 04:40:39 PM
Old 04-14-2009
No reason you have to use a "here script" with <<EOF, you can pipe commands directly to the standard input of ssh, for example using echo:

Code:
$ D=/tmp; F1=x1; echo "F2=$D/$F1
echo on \$(hostname): escaped: D=\$D F1=\$F1 F2=\$F2
echo on \$(hostname): not escaped: D=$D F1=$F1 F2=$F2
df $D >\$F2; ls -l \$F2; cat \$F2; rm -rf \$F2; ls -l \$F2
" | ssh qneill@qneill-linux

this shows a couple of local variables D and F1 (expanded locally when the local echo is executed), and a remote variable F2 (expands to nothing locally, but remotely expands to the assigned value). The commands produce this output:

Code:
on qneill-linux: escaped: D= F1= F2=/tmp/x1
on qneill-linux: not escaped: D=/tmp F1=x1 F2=
-rw-r--r-- 1 qneill 30101 125 2009-04-14 15:25 /tmp/x1
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda1            147581948  78980980  61104240  57% /
ls: /tmp/x1: No such file or directory

The commands shown use the local variable D and remote variable F2, creating, using, and removing a file (/tmp/x1 on the remote machine).

If all of your variable expansions are constant, or only depend on remote things, you can use single quotes and avoid having to escape all the $ signs:

Code:
echo 'D=/tmp; F1=x1; F2=$D/$F1
echo on $(hostname): D=$D F1=$F1 F2=$F2
df $D >$F2; ls -l $F2; cat $F2; rm -rf $F2; ls -l $F2
' | ssh qneill@qneill-linux

which yields
Code:
on qneill-linux: D=/tmp F1=x1 F2=/tmp/x1
-rw-r--r-- 1 qneill 30101 125 2009-04-14 15:34 /tmp/x1
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda1            147581948  78980960  61104260  57% /
ls: /tmp/x1: No such file or directory

Once you start using this mechanism for anything complicated, you will quickly run into many quoting issues. Consider writing a script that generates code on the remote system, or a templated script that can be parameterized locally or remotely as needed, then executed remotely with a single call to ssh.
--
qneill
 

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LEARN ABOUT OSX

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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