+ <title>Command lines</title>
+
+ <para>This section describes command line parsing and
+ variable and specifier substitions for
+ <varname>ExecStart=</varname>,
+ <varname>ExecStartPre=</varname>,
+ <varname>ExecStartPost=</varname>,
+ <varname>ExecReload=</varname>,
+ <varname>ExecStop=</varname>, and
+ <varname>ExecStopPost=</varname> options.</para>
+
+ <para>Multiple command lines may be concatenated in a
+ single directive by separating them with semicolons
+ (these semicolons must be passed as separate words).
+ Lone semicolons may be escaped as
+ <literal>\;</literal>.</para>
+
+ <para>Each command line is split on whitespace, with
+ the first item being the command to execute, and the
+ subsequent items being the arguments. Double quotes
+ ("...") and single quotes ('...') may be used, in
+ which case everything until the next matching quote
+ becomes part of the same argument. Quotes themselves
+ are removed after parsing. In addition, a trailing
+ backslash (<literal>\</literal>) may be used to merge
+ lines. </para>
+
+ <para>This syntax is intended to be very similar to
+ shell syntax, but only the meta-characters and
+ expansions described in the following paragraphs are
+ understood. Specifically, redirection using
+ <literal><</literal>, <literal><<</literal>,
+ <literal>></literal>, and
+ <literal>>></literal>, pipes using
+ <literal>|</literal>, running programs in the
+ background using <literal>&</literal>, and
+ <emphasis>other elements of shell syntax are not
+ supported</emphasis>.</para>
+
+ <para>The command line accepts <literal>%</literal>
+ specifiers as described in
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ Note that the first argument of the command line
+ (i.e. the program to execute) may not include
+ specifiers.</para>
+
+ <para>Basic environment variable substitution is
+ supported. Use <literal>${FOO}</literal> as part of a
+ word, or as a word of its own, on the command line, in
+ which case it will be replaced by the value of the
+ environment variable including all whitespace it
+ contains, resulting in a single argument. Use
+ <literal>$FOO</literal> as a separate word on the
+ command line, in which case it will be replaced by the
+ value of the environment variable split at whitespace
+ resulting in zero or more arguments. For this type of
+ expansion, quotes and respected when splitting into
+ words, and afterwards removed.</para>
+
+ <para>Example:</para>
+
+ <programlisting>Environment="ONE=one" 'TWO=two two'
+ExecStart=/bin/echo $ONE $TWO ${TWO}</programlisting>
+
+ <para>This will execute <command>/bin/echo</command>
+ with four arguments: <literal>one</literal>,
+ <literal>two</literal>, <literal>two</literal>, and
+ <literal>two two</literal>.</para>
+
+ <para>Example:</para>
+ <programlisting>Environment=ONE='one' "TWO='two two' too" THREE=
+ExecStart=/bin/echo ${ONE} ${TWO} ${THREE}
+ExecStart=/bin/echo $ONE $TWO $THREE</programlisting>
+ <para>This results in <filename>echo</filename> being
+ called twice, the first time with arguments
+ <literal>'one'</literal>,
+ <literal>'two two' too</literal>, <literal></literal>,
+ and the second time with arguments
+ <literal>one</literal>, <literal>two two</literal>,
+ <literal>too</literal>.
+ </para>