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110 lines
3.9 KiB
ReStructuredText
110 lines
3.9 KiB
ReStructuredText
Mixing with other languages
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================================================================
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As discussed in the section on :doc:`file-formats`, Miller supports several different file formats. Different tools are good at different things, so it's important to be able to move data into and out of other languages. **CSV** and **JSON** are well-known, of course; here are some examples using **DKVP** format, with **Ruby** and **Python**. Last, we show how to use arbitrary **shell commands** to extend functionality beyond Miller's domain-specific language.
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DKVP I/O in Python
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----------------------------------------------------------------
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Here are the I/O routines:
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::
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POKI_INCLUDE_ESCAPED(polyglot-dkvp-io/dkvp_io.py)HERE
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And here is an example using them:
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::
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POKI_RUN_COMMAND{{cat polyglot-dkvp-io/example.py}}HERE
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Run as-is:
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::
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POKI_RUN_COMMAND{{python polyglot-dkvp-io/example.py < data/small}}HERE
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Run as-is, then pipe to Miller for pretty-printing:
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::
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POKI_RUN_COMMAND{{python polyglot-dkvp-io/example.py < data/small | mlr --opprint cat}}HERE
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DKVP I/O in Ruby
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----------------------------------------------------------------
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Here are the I/O routines:
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::
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POKI_INCLUDE_ESCAPED(polyglot-dkvp-io/dkvp_io.rb)HERE
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And here is an example using them:
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::
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POKI_RUN_COMMAND{{cat polyglot-dkvp-io/example.rb}}HERE
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Run as-is:
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::
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POKI_RUN_COMMAND{{ruby -I./polyglot-dkvp-io polyglot-dkvp-io/example.rb data/small}}HERE
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Run as-is, then pipe to Miller for pretty-printing:
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::
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POKI_RUN_COMMAND{{ruby -I./polyglot-dkvp-io polyglot-dkvp-io/example.rb data/small | mlr --opprint cat}}HERE
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SQL-output examples
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----------------------------------------------------------------
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Please see :ref:`sql-output-examples`.
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SQL-input examples
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----------------------------------------------------------------
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Please see :ref:`sql-input-examples`.
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Running shell commands
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----------------------------------------------------------------
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The :ref:`reference-dsl-system` DSL function allows you to run a specific shell command and put its output -- minus the final newline -- into a record field. The command itself is any string, either a literal string, or a concatenation of strings, perhaps including other field values or what have you.
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::
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POKI_RUN_COMMAND{{mlr --opprint put '$o = system("echo hello world")' data/small}}HERE
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::
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POKI_RUN_COMMAND{{mlr --opprint put '$o = system("echo {" . NR . "}")' data/small}}HERE
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::
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POKI_RUN_COMMAND{{mlr --opprint put '$o = system("echo -n ".$a."| sha1sum")' data/small}}HERE
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Note that running a subprocess on every record takes a non-trivial amount of time. Comparing asking the system ``date`` command for the current time in nanoseconds versus computing it in process:
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..
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hard-coded, not live-code, since %N doesn't exist on all platforms
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::
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$ mlr --opprint put '$t=system("date +%s.%N")' then step -a delta -f t data/small
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a b i x y t t_delta
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pan pan 1 0.3467901443380824 0.7268028627434533 1568774318.513903817 0
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eks pan 2 0.7586799647899636 0.5221511083334797 1568774318.514722876 0.000819
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wye wye 3 0.20460330576630303 0.33831852551664776 1568774318.515618046 0.000895
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eks wye 4 0.38139939387114097 0.13418874328430463 1568774318.516547441 0.000929
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wye pan 5 0.5732889198020006 0.8636244699032729 1568774318.517518828 0.000971
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::
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$ mlr --opprint put '$t=systime()' then step -a delta -f t data/small
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a b i x y t t_delta
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pan pan 1 0.3467901443380824 0.7268028627434533 1568774318.518699 0
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eks pan 2 0.7586799647899636 0.5221511083334797 1568774318.518717 0.000018
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wye wye 3 0.20460330576630303 0.33831852551664776 1568774318.518723 0.000006
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eks wye 4 0.38139939387114097 0.13418874328430463 1568774318.518727 0.000004
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wye pan 5 0.5732889198020006 0.8636244699032729 1568774318.518730 0.000003
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