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