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Top Forums Shell Programming and Scripting Brace expansion problem in Bash Post 302330871 by mglenney on Thursday 2nd of July 2009 03:15:16 PM
Old 07-02-2009
Brace expansion problem in Bash

I have a script that takes an option for server pools to run the script against. The option is given as a comma separated list (ie, -p 201,204,301).

I'm using eval and brace expansion to get those pool numbers into an array. It works fine unless only 1 pool number is given. Here's the code:

Code:
while [ "$1" != "" ]; do
  case $1 in
    -p  )               shift
                        pools=($(for i in $(eval echo {$1}); do echo $i; done | sort))
                        ;;

If multiple pools given:

Code:
[me@server bin]$ ./project_nunenhoffen.sh -p 201,202
+ '[' -p '!=' '' ']'
+ case $1 in
+ shift
+ pools=($(for i in $(eval echo {$1}); do echo $i; done | sort))
++ sort
+++ eval echo '{201,202}'
++++ echo 201 202
++ for i in '$(eval echo {$1})'
++ echo 201
++ for i in '$(eval echo {$1})'
++ echo 202
+ shift
+ '[' '' '!=' '' ']'

If single pool given:

Code:
[me@server bin]$ ./project_nunenhoffen.sh -p 201
+ '[' -p '!=' '' ']'
+ case $1 in
+ shift
+ pools=($(for i in $(eval echo {$1}); do echo $i; done | sort))
++ sort
+++ eval echo '{201}'
++++ echo '{201}'
++ for i in '$(eval echo {$1})'
++ echo '{201}'
+ shift
+ '[' '' '!=' '' ']'

So if a single pool is given it leaves the braces around it which is bad. I could do a test of $1 to see if there are any commas and process it different if there aren't but I was wondering if there's a better solution than that. Also wondering if how I handled getting the pool numbers into an array was the best way to do it (eval & brace expansion).

Thanks,

Mike G.
 

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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)
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