escape(1)

NAME

escape - escape shell special characters in a string

escape string

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

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"`

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

David Mazieres