escape - Online in the Cloud

PROGRAM:

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"`

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