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How to filter a null variable.

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Top Forums Shell Programming and Scripting How to filter a null variable.
# 1  
Old 12-19-2003
Network How to filter a null variable.
I have the necessity to use this command:

cat file1 | grep $A | grep $B

where sometime A and, or, B are not set.

For example:
I set A=@
never defined or set B

The above command send a cat error.

Any idea?
Thanks.

Giovanni
# 2  
Old 12-19-2003
2 things.

check out egrep.

cat file|egrep $A\|$B

when you declare $A or $B if you use a meta charicter make sure you backslash it to remove its special meaning.

Code:
[qgatu003]/export/home/mxdooley$cat test.file|egrep $A\|$B
@this is a test2
[qgatu003]/export/home/mxdooley$echo $A
@
[qgatu003]/export/home/mxdooley$

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