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Document type stdin inside loop caveats

5.1
Darko Poljak 3 years ago
parent
commit
68837e45cc
  1. 1
      docs/changelog
  2. 67
      docs/src/cdist-type.rst

1
docs/changelog

@ -4,6 +4,7 @@ Changelog
next:
* Type __apt_key: Use gpg key, fallback to deprecated apt-key (Ander Punnar)
* Type __acl: Fix and improve (Ander Punnar)
* Documentation: Document type stdin inside loop caveats (Darko Poljak)
5.1.0: 2019-05-22
* Type __consul: Add alpine support (Nico Schottelius)

67
docs/src/cdist-type.rst

@ -216,6 +216,73 @@ In the __file type, stdin is used as source for the file, if - is used for sourc
....
Stdin inside a loop
~~~~~~~~~~~~~~~~~~~
Since cdist saves type's stdin content in the object as **$__object/stdin**,
so it can be accessed in manifest and gencode-* scripts, this can lead to
unexpected behavior. For example, suppose you have some type with the following
in its manifest:
.. code-block:: sh
if [ -f "$__object/parameter/foo" ]
then
while read -r l
do
__file "$l"
echo "$l" >&2
done < "$__object/parameter/foo"
fi
and init manifest:
.. code-block:: sh
__foo foo --foo a --foo b --foo c
You expect that manifest stderr content is:
.. code-block:: sh
a
b
c
and that files *a*, *b* and *c* are created. But all you get in manifest stderr
is:
.. code-block:: sh
a
and only *a* file is created.
When redirecting parameter *foo* file content to while's stdin that means that all
commands in while body have this same stdin. So when *__file* type gets executed,
cdist saves its stdin which means it gets the remaining content of parameter *foo*
file, i.e.:
.. code-block:: sh
b
c
The solution is to make sure that your types inside such loops get their stdin
from somewhere else, e.g. for the above problem *__file* type can get empty
stdin from */dev/null*:
.. code-block:: sh
if [ -f "$__object/parameter/foo" ]
then
while read -r l
do
__file "$l" < /dev/null
echo "$l" >&2
done < "$__object/parameter/foo"
fi
Writing the manifest
--------------------
In the manifest of a type you can use other types, so your type extends

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