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Full Discussion: Eval
Top Forums Shell Programming and Scripting Eval Post 302802537 by Corona688 on Friday 3rd of May 2013 04:39:58 PM
Old 05-03-2013
Yes, exactly. It does the normal substitution step like any other shell command, then starts over.

You have shell variables in your sql file, even though it's not a shell script? Yeah, that's awkward.

One way to substitute would be to put it all into a here-document like this:

Code:
cat <<EOF
This will print everything up to an EOF at the beginning of the line
${variables} and `echo backticks` are substituted, but
commands are not.  You can \${escape} them to get the literal characters.
EOF

This takes the big SQL file, puts cat <<__EOF___ at the front of it, __EOF__ at the end of it, escapes ` and $( and \, prevents people from sneaking out of the here-document with their own __EOF__, and runs it in a shell. It will swallow the entire text nearly raw, substituting variables and nothing else. Results in /tmp/converted, or you can use them directly via a pipe.

Code:
echo "cat <<___EOF___" > /tmp/script
sed 's/\\/\\\\/g;s/`/\\`/g;s/^___EOF___/ ___EOF___/' /path/to/sql >> /tmp/script
echo "___EOF___" >> /tmp/script

/bin/sh /tmp/script > /tmp/converted
rm -f /tmp/script

This would be far less risky than eval -- less risk of malicious use, and less risk of accidental syntax errors due to embedded ' " | ` ( ) &
Last edited by Corona688; 05-03-2013 at 05:51 PM..
 

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LEARN ABOUT DEBIAN

safe_asterisk

SAFE_ASTERISK(8)					     Linux Programmer's Manual						  SAFE_ASTERISK(8)

NAME

       safe_asterisk -- A wrapper to run the asterisk executable in a loop

SYNOPSIS

       safe_asterisk [ asterisk_params ]

DESCRIPTION

       safe_asterisk is a script that runs asterisk in a loop, which can be useful if you fear asterisk may crash.

       The  script  does  not run in the background like a standard service. Rather, it runs in its own linux virtual console (9, by default).	It
       also uses the option '-c' of asterisk(8) to avoid detaching asterisk from that terminal.

       safe_asterisk also runs asterisk with unlimited core file size, and thus asterisk will dump core in case of a crash.

       To get a "picture" of console 9, from another terminal (e.g: from a remote shell session) you can use:

	 screendump 9

       The init script of the Debian package should be able to run safe_asterisk as the  asterisk  service,  if  so  configured.  See  coments	in
       /etc/default/asterisk

FILES

       /tmp
	      safe_asterisk runs in that directory, rather than in / as usual.

       /tmp/core
	      If core files were generated there, they may be

       /etc/asterisk/startup.d
	      Files  in  this directory will be 'source'd by the safe_asterisk script before it starts Asterisk proper, allowing them to set addi-
	      tional environment variables or run any other steps that are needed for your system.

BUGS

       While showing the output on a console is useful, using screen(1) as the terminal may be better.

       The script does not read configuration from standard location under /etc

       It uses fixed locations under /tmp , and thus may be exposed to a symlink attacks.

SEE ALSO

       asterisk(8), screendump(9)

AUTHOR

       This manual page was written by Tzafrir Cohen <tzafrir.cohen@xorcom.com> Permission is granted to copy, distribute and/or modify this docu-
       ment under the terms of the GNU General Public License, Version 2 any later version published by the Free Software Foundation.

       On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL-2.

Asterisk							  Jun 30th, 2005						  SAFE_ASTERISK(8)
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