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Document new PIPE_ONCE macro

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Lorin Hochstein 2013-02-17 12:47:51 -05:00
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commit ec16b854a5
1 changed files with 18 additions and 6 deletions
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docsite/rst/playbooks2.rst
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@ -583,6 +583,18 @@ is an example using the authorized_key module, which requires the actual text of
The "$PIPE" macro works just like file, except you would feed it a command string instead. It executes locally, not remotely, as does $FILE. The "$PIPE" macro works just like file, except you would feed it a command string instead. It executes locally, not remotely, as does $FILE.
Because Ansible uses lazy evaluation, a "$PIPE" macro will be executed each time it is used. For
example, it will be executed separately for each host, and if it is used in a variable definition,
it will be executed each time the variable is evaluated.
The "$PIPE_ONCE" macro is an alternative that uses a caching strategy: it is executed only once, and
subsequent accesses use the cached value. One use case is for computing a timestamp that is intended
to be the same across all tasks and hosts that use it::
vars:
timestamp: $PIPE_ONCE(date +%Y%m%d-%H%M%S)
Selecting Files And Templates Based On Variables Selecting Files And Templates Based On Variables
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