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What's the difference between $* and $@ ?

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# 1  
Old 04-17-2012
What's the difference between $* and $@ ?
What's the difference between $* and $@?
And I read that the $* has security problems, why?
# 2  
Old 04-17-2012
When I call this file
Code:
#!/bin/bash

echo -e "With \$* I have to chose all or nothing"
echo "ALL"
for i in "$*" ; do
    echo -e "\t$i"
done
echo  "NOTHING"
for i in $* ; do
    echo -e "\t$i"
done
echo -e "Whereas with \$@ I get my parameters as the user intended (or at any rate as they sent them to me ;) )"
for i in "$@" ; do
    echo -e "\t$i"
done

as follows
Code:
~/tmp/tmp.sh "It is vital this remains intact" but that these are separate parameters

I get the following
Code:
With $* I have to chose all or nothing
ALL
  It is vital this remains intact but that these are separate parameters
NOTHING
  It
  is
  vital
  this
  remains
  intact
  but
  that
  these
  are
  separate
  parameters
Whereas with $@ I get my parameters as the user intended (or at any rate as they sent them to me ;) )
  It is vital this remains intact
  but
  that
  these
  are
  separate
  parameters

Does that make things clearer?
These 2 Users Gave Thanks to Skrynesaver For This Post:
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# 3  
Old 04-17-2012
Regarding the security aspect, what is probably meant by this is that $@ can be expanded into separate fields each within double quotes, thus protecting the fields from unwanted interpretation by the shell. With $* this is only possible without double quotes and so there is no protection.
Last edited by Scrutinizer; 04-17-2012 at 11:59 AM..
This User Gave Thanks to Scrutinizer For This Post:
Henryyy
# 4  
Old 04-17-2012
Quote:
Originally Posted by Scrutinizer
Regarding the security aspect, what is probably meant by this is that $@ can be expanded into separate fields each within double quotes, thus protecting the fields from unwanted interpretation by the shell. With $* this is only possible without double quotes and so there is no protection.
And fields which contain $IFS are split when exposed without double quotes.
# 5  
Old 04-17-2012
Of course, it's only a security problem when the splitting is unintentional. It has its uses when splitting intentionally, especially since you can control what it splits on with IFS...
# 6  
Old 04-17-2012
That's a GREAT example!
# 7  
Old 04-18-2012
Very clear, thank you very much!
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