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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 CENTOS

err_get_reason

ERR_GET_LIB(3)							      OpenSSL							    ERR_GET_LIB(3)

NAME

       ERR_GET_LIB, ERR_GET_FUNC, ERR_GET_REASON - get library, function and reason code

SYNOPSIS

	#include <openssl/err.h>

	int ERR_GET_LIB(unsigned long e);

	int ERR_GET_FUNC(unsigned long e);

	int ERR_GET_REASON(unsigned long e);

DESCRIPTION

       The error code returned by ERR_get_error() consists of a library number, function code and reason code. ERR_GET_LIB(), ERR_GET_FUNC() and
       ERR_GET_REASON() can be used to extract these.

       The library number and function code describe where the error occurred, the reason code is the information about what went wrong.

       Each sub-library of OpenSSL has a unique library number; function and reason codes are unique within each sub-library.  Note that different
       libraries may use the same value to signal different functions and reasons.

       ERR_R_... reason codes such as ERR_R_MALLOC_FAILURE are globally unique. However, when checking for sub-library specific reason codes, be
       sure to also compare the library number.

       ERR_GET_LIB(), ERR_GET_FUNC() and ERR_GET_REASON() are macros.

RETURN VALUES

       The library number, function code and reason code respectively.

SEE ALSO

       err(3), ERR_get_error(3)

HISTORY

       ERR_GET_LIB(), ERR_GET_FUNC() and ERR_GET_REASON() are available in all versions of SSLeay and OpenSSL.

1.0.1e								    2013-02-11							    ERR_GET_LIB(3)
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