Parsing

Nu offers the ability to do some basic parsing, with different ways to achieve the same goal.

Builtin-functions that can be used include:

  • lines
  • detect columns
  • parse
  • str ...
  • from ssv

A few illustrative examples follow.

Examples (tabular output)

detect columns (pretty automatic)

df -h | str replace "Mounted on" Mounted_On | detect columns
# => ╭────┬───────────────────────────────────┬──────┬──────┬───────┬──────┬────────────────────────────────────╮
# => │  # │            Filesystem             │ Size │ Used │ Avail │ Use% │             Mounted_On             │
# => ├────┼───────────────────────────────────┼──────┼──────┼───────┼──────┼────────────────────────────────────┤
# => │  0 │ devtmpfs                          │ 3.2G │ 0    │ 3.2G  │ 0%   │ /dev                               │
# => │  1 │ tmpfs                             │ 32G  │ 304M │ 32G   │ 1%   │ /dev/shm                           │
# => │  2 │ tmpfs                             │ 16G  │ 11M  │ 16G   │ 1%   │ /run                               │
# => │  3 │ tmpfs                             │ 32G  │ 1.2M │ 32G   │ 1%   │ /run/wrappers                      │
# => │  4 │ /dev/nvme0n1p2                    │ 129G │ 101G │ 22G   │ 83%  │ /                                  │
# => │  5 │ /dev/nvme0n1p8                    │ 48G  │ 16G  │ 30G   │ 35%  │ /var                               │
# => │  6 │ efivarfs                          │ 128K │ 24K  │ 100K  │ 20%  │ /sys/firmware/efi/efivars          │
# => │  7 │ tmpfs                             │ 32G  │ 41M  │ 32G   │ 1%   │ /tmp                               │
# => │  8 │ /dev/nvme0n1p3                    │ 315G │ 230G │ 69G   │ 77%  │ /home                              │
# => │  9 │ /dev/nvme0n1p1                    │ 197M │ 120M │ 78M   │ 61%  │ /boot                              │
# => │ 10 │ /dev/mapper/vgBigData-lvBigData01 │ 5.5T │ 4.1T │ 1.1T  │ 79%  │ /bigdata01                         │
# => │ 11 │ tmpfs                             │ 1.0M │ 4.0K │ 1020K │ 1%   │ /run/credentials/nix-serve.service │
# => │ 12 │ tmpfs                             │ 6.3G │ 32M  │ 6.3G  │ 1%   │ /run/user/1000                     │
# => ╰────┴───────────────────────────────────┴──────┴──────┴───────┴──────┴────────────────────────────────────╯

For an output like from df this is probably the most compact way to achieve a nice tabular output. The str replace is needed here because one of the column headers has a space in it. Alternatively, detect columns --guess works out the columns from their widths, so it keeps the Mounted on header intact without the str replace:

df -h | detect columns --guess

Using from ssv

Also the builtin from data parser for ssv (space separated values) can be used:

df -h | str replace "Mounted on" Mounted_On | from ssv --aligned-columns --minimum-spaces 1

The output is identical to the previous example.

from ssv supports several modifying flags to tweak its behaviour.

Note we still need to fix the column headers if they contain unexpected spaces.

Using parse

How to parse an arbitrary pattern from a string of text into a multi-column table.

cargo search shells --limit 10 | lines | parse "{crate_name} = {version} #{description}" | str trim
# => ╭───┬─────────────────────────┬──────────┬─────────────────────────────────────────────────────────╮
# => │ # │       crate_name        │ version  │                       description                       │
# => ├───┼─────────────────────────┼──────────┼─────────────────────────────────────────────────────────┤
# => │ 0 │ shells                  │ "0.2.0"  │ Sugar-coating for invoking shell commands directly from │
# => │   │                         │          │  Rust.                                                  │
# => │ 1 │ virtiofsd               │ "1.14.0" │ A virtio-fs vhost-user device daemon                    │
# => │ 2 │ hurl                    │ "8.0.1"  │ Hurl, run and test HTTP requests                        │
# => │ 3 │ shell-quote             │ "0.8.0"  │ A Rust library for shell-quoting strings, e.g. for      │
# => │   │                         │          │ interpolating into a Bash script.                       │
# => │ 4 │ coreutils               │ "0.12.0" │ coreutils ~ GNU coreutils (updated); implemented as     │
# => │   │                         │          │ universal (cross-platform) utils, wri…                  │
# => │ 5 │ command-stream          │ "1.1.0"  │ Modern shell command execution library with streaming,  │
# => │   │                         │          │ async iteration, and event support                      │
# => │ 6 │ datafusion-sqllogictest │ "55.1.0" │ DataFusion sqllogictest driver                          │
# => │ 7 │ skim                    │ "5.7.2"  │ Fuzzy Finder in rust!                                   │
# => │ 8 │ bashrs                  │ "7.4.1"  │ Rust-to-Shell transpiler for deterministic bootstrap    │
# => │   │                         │          │ scripts                                                 │
# => │ 9 │ shell-words             │ "1.1.1"  │ Process command line according to parsing rules of UNIX │
# => │   │                         │          │  shell                                                  │
# => ╰───┴─────────────────────────┴──────────┴─────────────────────────────────────────────────────────╯