man/systemd-service: clarify env variable expansion

This clarifies some more aspects of `${FOO}` expansions in service
units, mostly trying to answer my own doubts about what happens when
the matching variable is not defined.
This commit is contained in:
Luca BRUNO 2020-04-16 13:28:18 +00:00 committed by Lennart Poettering
parent f3a604e4cf
commit 3db1c62d22
1 changed files with 4 additions and 4 deletions

View File

@ -1106,10 +1106,10 @@
<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
own, on the command line, in which case it will be erased and replaced
by the exact value of the environment variable (if any) including all
whitespace it contains, always resulting in exactly 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 are respected when splitting