.\" (C) Copyright 2011-2024 Software Freedom Conservancy, Inc.
.\" This program is free software; you can redistribute it and/or modify
.\" it under the terms of the GNU General Public License as published by
.\" the Free Software Foundation; either version 3 of the License, or
.\" (at your option) any later version.
.\"
.TH "DH\-EXEC\-SUBST" "1" "2024-02-27" "" "dh-exec"
.ad l
.nh
.SH "NAME"
dh\-exec\-subst \- Debhelper executable file substition scripts
.SH "SYNOPSIS"
\fB#! /usr/bin/dh\-exec\fR
.br
src/libfoo-*.so.* debian/foo-plugins/usr/lib/foo/${DEB_HOST_MULTIARCH}/

.SH "DESCRIPTION"
Being a sub\-command of
.BR dh\-exec (1),
this program must not be
ran directly, but through \fIdh\-exec\fR, which automatically runs all
available sub\-commands if run bare; or explicitly with \fBdh\-exec
\-\-with=subst\fR.

It is a wrapper around the various other substitution helpers, and
will pipe the input file through all the available substitution
helpers. It is up to these scripts to do the actual work.

When a helper fails to expand a variable within its input, it will
leave it as-is, so that later in the pipeline it can perhaps be
expanded by another program.

.SH "SCRIPTS"

.TP
.B dh\-exec\-subst\-env
Substitutes any of the available, exported environment variables into
its input. It does not do any kind of filtering: whatever is available
in the environment, will be available for substitution, however unsafe
that may be.

\fB${FOO}\fR and \fB${env:FOO}\fR both will expand to the environment
variable \fIFOO\fR. Only the \fBenv\fR form will error if the
variable is unset, in keeping with
.BR debhelper (7)
convention.

Introduced in version \fI0.1\fR, with the \fBenv:\fR format added
in \fI0.29\fR.

.TP
.B dh\-exec\-subst\-multiarch
Attempts to expand any of the variables known to
.BR dpkg\-architecture (1),
mostly useful for multi\-arch support.

The command will query \fBdpkg\-architecture\fR(1) directly, and does
not rely on environment variables set (as the called program will
prefer already set environment variables anyway).

Introduced in version \fI0.1\fR.

.SH "ENVIRONMENT"
.PP
\fIDH_EXEC_SCRIPTDIR\fR
.RS 4
Indicates which directory the command\-specific scripts should be
sought for. If not specified, scripts will be searched for in
\fI/usr/share/dh\-exec/\fR.
.RE

.SH "FILES"
.PP
\fI$DH_EXEC_SCRIPTDIR/dh\-exec\-subst\-*\fR
.RS 4
The various scripts for the higher\-level program.
.RE

.SH "VERSIONS"

The sub\-command was introduced in dh\-exec version \fI0.1\fR.

.SH "SEE ALSO"
.BR dh\-exec (1),
.BR dpkg\-architecture (1),
.BR debhelper (7)