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.\" ========================================================================
.\"
.IX Title "escape 1"
.TH escape 1 "2018-10-09" "Mail Avenger 0.8.5" "Mail Avenger 0.8.5"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
escape \- escape shell special characters in a string
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
escape \fIstring\fR
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
escape prepends a \f(CW\*(C`\e\*(C'\fR character to all shell special characters in
\&\fIstring\fR, making it safe to compose a shell command with the result.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
The following is a contrived example showing how one can
unintentionally end up executing the contents of a string:
.PP
.Vb 5
\&    $ var=\*(Aq; echo gotcha!\*(Aq
\&    $ eval echo hi $var
\&    hi
\&    gotcha!
\&    $
.Ve
.PP
Using escape, one can avoid executing the contents of \f(CW$var\fR:
.PP
.Vb 3
\&    $ eval echo hi \`escape "$var"\`
\&    hi ; echo gotcha!
\&    $
.Ve
.PP
A less contrived example is passing arguments to Mail Avenger bodytest
commands containing possibly unsafe environment variables.  For
example, you might write a hypothetical \fIreject_bcc\fR script to reject
mail not explicitly addressed to the recipient:
.PP
.Vb 6
\&    #!/bin/sh
\&    formail \-x to \-x cc \-x resent\-to \-x resent\-cc \e
\&        | fgrep "$1" > /dev/null \e
\&            && exit 0
\&    echo "<$1>.. address does not accept blind carbon copies"
\&    exit 100
.Ve
.PP
To invoke this script, passing it the recipient address as an
argument, you would need to put the following in your Mail Avenger
\&\fIrcpt\fR script:
.PP
.Vb 1
\&    bodytest reject_bcc \`escape "$RECIPIENT"\`
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBavenger\fR\|(1),
.PP
The Mail Avenger home page: <http://www.mailavenger.org/>.
.SH "BUGS"
.IX Header "BUGS"
escape is designed for the Bourne shell, which is what Mail Avenger
scripts use.  escape might or might not work with other shells.
.SH "AUTHOR"
.IX Header "AUTHOR"
David Mazie\*`res