nushell/docs/commands/from-csv.md
Jörn Zaefferer 8ab2b92405
docs/commands: add from.md, update subcommands (#1712)
This adds a top-level document for the new `from` command, with a list of links of all the subcommands.

All the from-* subcommands keep their filename, but the content is updated to use the new subcommand syntax.

Needs matching update for to*

Ref #1709
2020-05-05 09:01:31 +12:00

117 lines
3.8 KiB
Markdown

# from csv
Converts csv data into table. Use this when nushell cannot determine the input file extension.
## Example
Let's say we have the following file :
```shell
> cat pets.txt
animal, name, age
cat, Tom, 7
dog, Alfred, 10
chameleon, Linda, 1
```
`pets.txt` is actually a .csv file but it has the .txt extension, `open` is not able to convert it into a table :
```shell
> open pets.txt
animal, name, age
cat, Tom, 7
dog, Alfred, 10
chameleon, Linda, 1
```
To get a table from `pets.txt` we need to use the `from csv` command :
```shell
> open pets.txt | from csv
━━━┯━━━━━━━━━━━┯━━━━━━━━━┯━━━━━━
# │ animal │ name │ age
───┼───────────┼─────────┼──────
0 │ cat │ Tom │ 7
1 │ dog │ Alfred │ 10
2 │ chameleon │ Linda │ 1
━━━┷━━━━━━━━━━━┷━━━━━━━━━┷━━━━━━
```
To ignore the csv headers use `--headerless` :
```shell
━━━┯━━━━━━━━━━━┯━━━━━━━━━┯━━━━━━━━━
# │ Column1 │ Column2 │ Column3
───┼───────────┼─────────┼─────────
0 │ dog │ Alfred │ 10
1 │ chameleon │ Linda │ 1
━━━┷━━━━━━━━━━━┷━━━━━━━━━┷━━━━━━━━━
```
To split on a character other than ',' use `--separator` :
```shell
> open pets.txt
animal; name; age
cat; Tom; 7
dog; Alfred; 10
chameleon; Linda; 1
```
```shell
> open pets.txt | from csv --separator ';'
━━━┯━━━━━━━━━━━┯━━━━━━━━━┯━━━━━━
# │ animal │ name │ age
───┼───────────┼─────────┼──────
0 │ cat │ Tom │ 7
1 │ dog │ Alfred │ 10
2 │ chameleon │ Linda │ 1
━━━┷━━━━━━━━━━━┷━━━━━━━━━┷━━━━━━
```
To use this command to open a csv with separators other than a comma, use the `--raw` switch of `open` to open the csv, otherwise the csv will enter `from csv` as a table split on commas rather than raw text.
```shell
> mv pets.txt pets.csv
> open pets.csv | from csv --separator ';'
error: Expected a string from pipeline
- shell:1:16
1 | open pets.csv | from csv --separator ';'
| ^^^^^^^^ requires string input
- shell:1:0
1 | open pets.csv | from csv --separator ';'
| value originates from here
> open pets.csv --raw | from csv --separator ';'
━━━┯━━━━━━━━━━━┯━━━━━━━━━┯━━━━━━
# │ animal │ name │ age
───┼───────────┼─────────┼──────
0 │ cat │ Tom │ 7
1 │ dog │ Alfred │ 10
2 │ chameleon │ Linda │ 1
━━━┷━━━━━━━━━━━┷━━━━━━━━━┷━━━━━━
```
The string '\t' can be used to separate on tabs. Note that this is the same as using the from-tsv command.
Newlines '\n' are not acceptable separators.
Note that separators are currently provided as strings and need to be wrapped in quotes.
```shell
> open pets.csv --raw | from csv --separator ;
- shell:1:43
1 | open pets.csv --raw | from csv --separator ;
| ^
```
It is also considered an error to use a separator greater than one char :
```shell
> open pets.txt | from csv --separator '123'
error: Expected a single separator char from --separator
- shell:1:37
1 | open pets.txt | from csv --separator '123'
| ^^^^^ requires a single character string input
```