Keystroke-savers - Miller

<div> Quick links:   <a class="quicklink" href="../reference-main-flag-list/index.html">Flags</a>   <a class="quicklink" href="../reference-verbs/index.html">Verbs</a>   <a class="quicklink" href="../reference-dsl-builtin-functions/index.html">Functions</a>   <a class="quicklink" href="../glossary/index.html">Glossary</a>   <a class="quicklink" href="../release-docs/index.html">Release docs</a> </div> # Keystroke-savers

Short format specifiers, including --c2p

In our examples so far, we've often made use of mlr --icsv --opprint or mlr --icsv --ojson. These are such frequently occurring patterns that they have short options like --c2p and --c2j:

<pre class="pre-highlight-in-pair"> mlr --c2p head -n 2 example.csv </pre> <pre class="pre-non-highlight-in-pair"> color shape flag k index quantity rate yellow triangle true 1 11 43.6498 9.8870 red square true 2 15 79.2778 0.0130 </pre> <pre class="pre-highlight-in-pair"> mlr --c2j head -n 2 example.csv </pre> <pre class="pre-non-highlight-in-pair"> [ { "color": "yellow", "shape": "triangle", "flag": "true", "k": 1, "index": 11, "quantity": 43.6498, "rate": 9.8870 }, { "color": "red", "shape": "square", "flag": "true", "k": 2, "index": 15, "quantity": 79.2778, "rate": 0.0130 } ] </pre>

You can get the full list here.

File names up front, including --from

Already, we saw that you can put the filename first using --from. When you're interacting with your data at the command line, this makes it easier to up-arrow and append to the previous command:

<pre class="pre-highlight-in-pair"> mlr --c2p --from example.csv sort -nr index then head -n 3 </pre> <pre class="pre-non-highlight-in-pair"> color shape flag k index quantity rate purple square false 10 91 72.3735 8.2430 yellow circle true 9 87 63.5058 8.3350 yellow circle true 8 73 63.9785 4.2370 </pre> <pre class="pre-highlight-in-pair"> mlr --c2p --from example.csv sort -nr index then head -n 3 then cut -f shape,quantity </pre> <pre class="pre-non-highlight-in-pair"> shape quantity square 72.3735 circle 63.5058 circle 63.9785 </pre>

If there's more than one input file, you can use --mfrom, then however many file names, then -- to indicate the end of your input-file-name list:

<pre class="pre-highlight-non-pair"> mlr --c2p --mfrom data/*.csv -- sort -n index </pre>

Alternatively, you may place filenames within another file, one per line:

<pre class="pre-highlight-non-pair"> cat data/filenames.txt </pre> <pre class="pre-highlight-non-pair"> mlr --c2p --files data/filenames.txt cat </pre>

Shortest flags for CSV, TSV, and JSON

The following have even shorter versions:

-c is the same as --csv
-t is the same as --tsv
-j is the same as --json

I don't use these within these documents, since I want the docs to be self-explanatory on every page, and I think mlr --csv ... explains itself better than mlr -c .... Nonetheless, they're always there for you to use.

.mlrrc file

If you want the default file format for Miller to be CSV, you can put --csv on a line by itself in your ~/.mlrrc file. Then, instead of mlr --csv cat example.csv you can just do mlr cat example.csv. This is just a personal default, though, so mlr --opprint cat example.csv will use default CSV format for input, and PPRINT (tabular) for output.

You can read more about this at the Customization page.

Scripts and mlr -s

Suppose you are often doing something like

<pre class="pre-non-highlight-non-pair"> mlr --csv \ filter ‘$quantity > 100’ then \ count-distinct -f category then \ fraction -f count \ filename-which-varies.csv </pre>

Typing this out can get a bit old if the only thing that changes for you is the filename.

See Scripting with Miller for some keystroke-saving options.