From: Russ Allbery <rra@debian.org>
Date: Tue, 1 Jun 2010 17:40:41 +0000 (-0700)
Subject: Except init.d scripts from the normal set -e requirement
X-Git-Url: https://git.donarmstrong.com/?a=commitdiff_plain;h=054029abead4996f10c2a97bf431db0bd95de44c;p=debian%2Fdebian-policy.git

Except init.d scripts from the normal set -e requirement

Mention init.d scripts as a special exception from the normal advise
to always use set -e in all shell scripts, and add a new paragraph to
the section on init.d scripts advising caution in using set -e and
explaining some of the issues.
---

diff --git a/policy.sgml b/policy.sgml
index d16df70..1871d4c 100644
--- a/policy.sgml
+++ b/policy.sgml
@@ -6011,7 +6011,7 @@ rmdir /usr/local/share/emacs 2>/dev/null || true
 	  </p>
 	</sect1>
 
-	<sect1>
+	<sect1 id="writing-init">
 	  <heading>Writing the scripts</heading>
 
 	  <p>
@@ -6061,6 +6061,23 @@ rmdir /usr/local/share/emacs 2>/dev/null || true
 	    option.
 	  </p>
 
+	  <p>
+	    Be careful of using <tt>set -e</tt> in <file>init.d</file>
+	    scripts.  Writing correct <file>init.d</file> scripts requires
+	    accepting various error exit statuses when daemons are already
+	    running or already stopped without aborting
+	    the <file>init.d</file> script, and common <file>init.d</file>
+	    function libraries are not safe to call with <tt>set -e</tt>
+	    in effect<footnote>
+	      <tt>/lib/lsb/init-functions</tt>, which assists in writing
+	      LSB-compliant init scripts, may fail if <tt>set -e</tt> is
+	      in effect and echoing status messages to the console fails,
+	      for example.
+	    </footnote>.  For <tt>init.d</tt> scripts, it's often easier
+	    to not use <tt>set -e</tt> and instead check the result of
+	    each command separately.
+	  </p>
+
 	  <p>
 	    If a service reloads its configuration automatically (as
 	    in the case of <prgn>cron</prgn>, for example), the
@@ -7158,13 +7175,19 @@ strip --strip-unneeded <var>your-lib</var>
           language currently used to implement it.
         </p>
 	<p>
-	  Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
-	  should almost certainly start with <tt>set -e</tt> so that
-	  errors are detected.  Every script should use
-	  <tt>set -e</tt> or check the exit status of <em>every</em>
-	  command.
+	  Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
+	  <file>init.d</file> scripts should almost certainly start
+	  with <tt>set -e</tt> so that errors are detected.
+	  <file>init.d</file> scripts are something of a special case, due
+	  to how frequently they need to call commands that are allowed to
+	  fail, and it may instead be easier to check the exit status of
+	  commands directly.  See <ref id="writing-init"> for more
+	  information about writing <file>init.d</file> scripts.
+	</p>
+	<p>
+	  Every script should use <tt>set -e</tt> or check the exit status
+	  of <em>every</em> command.
 	</p>
-
 	<p>
 	  Scripts may assume that <file>/bin/sh</file> implements the
 	  SUSv3 Shell Command Language<footnote>