miller/docs6/docs/keystroke-savers.md

Keystroke-savers

Short format specifiers

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:

mlr --c2p head -n 2 example.csv

color  shape    flag index quantity rate
yellow triangle true 11    43.6498  9.8870
red    square   true 15    79.2778  0.0130

mlr --c2j head -n 2 example.csv

{
  "color": "yellow",
  "shape": "triangle",
  "flag": true,
  "index": 11,
  "quantity": 43.6498,
  "rate": 9.8870
}
{
  "color": "red",
  "shape": "square",
  "flag": true,
  "index": 15,
  "quantity": 79.2778,
  "rate": 0.0130
}

You can get the full list here (TODO:linkify).

File names up front

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:

mlr --c2p --from example.csv sort -nr index then head -n 3

color  shape  flag  index quantity rate
purple square false 91    72.3735  8.2430
yellow circle true  87    63.5058  8.3350
yellow circle true  73    63.9785  4.2370

mlr --c2p --from example.csv sort -nr index then head -n 3 then cut -f shape,quantity

shape  quantity
square 72.3735
circle 63.5058
circle 63.9785

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:

mlr --c2p --mfrom data/*.csv -- sort -n index

.mlrrc file

If you want the default file format for Miller to be CSV you can simply 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 the default, though, so mlr --opprint cat example.csv will still use default CSV format for input, and PPRINT (tabular) for output.

You can read more about this at the Customization page.