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if [ -z echo foo | egrep -e 'regexp' != '' ] -> dont work

 
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Old 01-27-2009
if [ -z echo foo | egrep -e 'regexp' != '' ] -> dont work
Hallo,

I need to test a String (a special ip number-string).

So I want to run that:
Code:
ipadress=172.0.0.0

# for debugging:
echo $ipadress | egrep -e '172\.[0-9][0-9]?\.[0-9][0-9]?[0-9]?\.[0-9][0-9]?[0-9]?$'

# the test that doesnt work
if test -z `echo $ipadress | egrep -e '172\.[0-9][0-9]?\.[0-9][0-9]?[0-9]?\.[0-9][0-9]?[0-9]?$'` != ""
then
  echo "match"
else
  echo "dont match"
fi

When I run this, I get the message: "dont match"
But it matchs...

But when I run this:
Code:
ipadress=nothing

# for debugging:
echo $ipadress | egrep -e '172\.[0-9][0-9]?\.[0-9][0-9]?[0-9]?\.[0-9][0-9]?[0-9]?$'

# the test that doesnt work
if test -z `echo $ipadress | egrep -e '172\.[0-9][0-9]?\.[0-9][0-9]?[0-9]?\.[0-9][0-9]?[0-9]?$'` != ""
then
  echo "match"
else
  echo "dont match"
fi

I get the message: "match"

Thats not what I want! But What make I wrong?
 
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LEARN ABOUT V7

escape

escape(1)							Mail Avenger 0.8.3							 escape(1)

NAME

       escape - escape shell special characters in a string

SYNOPSIS

       escape string

DESCRIPTION

       escape prepends a "" character to all shell special characters in string, making it safe to compose a shell command with the result.

EXAMPLES

       The following is a contrived example showing how one can unintentionally end up executing the contents of a string:

	   $ var='; echo gotcha!'
	   $ eval echo hi $var
	   hi
	   gotcha!
	   $

       Using escape, one can avoid executing the contents of $var:

	   $ eval echo hi `escape "$var"`
	   hi ; echo gotcha!
	   $

       A less contrived example is passing arguments to Mail Avenger bodytest commands containing possibly unsafe environment variables.  For
       example, you might write a hypothetical reject_bcc script to reject mail not explicitly addressed to the recipient:

	   #!/bin/sh
	   formail -x to -x cc -x resent-to -x resent-cc 
	       | fgrep "$1" > /dev/null 
		   && exit 0
	   echo "<$1>.. address does not accept blind carbon copies"
	   exit 100

       To invoke this script, passing it the recipient address as an argument, you would need to put the following in your Mail Avenger rcpt
       script:

	   bodytest reject_bcc `escape "$RECIPIENT"`

SEE ALSO

       avenger(1),

       The Mail Avenger home page: <http://www.mailavenger.org/>.

BUGS

       escape is designed for the Bourne shell, which is what Mail Avenger scripts use.  escape might or might not work with other shells.

AUTHOR

       David Mazieres

Mail Avenger 0.8.3						    2012-04-05								 escape(1)