How-to guide

Choose the format aless reads

Read a file whose name does not tell its format, or standard input, as the format you name.

aless takes a file's format from its extension, and reads a file whose extension no format claims as plain text, an array of its lines. When the name is wrong or missing, you name the format.

Name the format of a file #

Give -k (or --kind, or --format) a format:

aless -k yaml deployment.conf
aless -k jsonl --paths --depth 1 events.log

-k applies to every file on the command line. In the viewer, :format yaml reads the focused tab again as YAML, and :open PATH FORMAT opens a file as the format you name.

Read standard input #

aless reads standard input when it is not a terminal, as JSON unless -k says otherwise:

$ printf 'name: aless\ntags: [viewer, cli]\n' | aless -k yaml --json --compact
{"name":"aless","tags":["viewer","cli"]}

- stands for standard input where a command takes files. Piped into the viewer, as in curl -s https://api.example/items | aless, the response opens in a tab of its own. On Windows the viewer needs a console to read keys from, so give it a file there rather than a pipe.

When the format is wrong #

A file read as the wrong format fails where the parse stops, with the status 1:

$ aless --kind json --json --compact bookshelf-openapi.yaml; echo $?
{"error":{"kind":"parse","file":"bookshelf-openapi.yaml","format":"json","code":"unexpected","message":"unexpected character(s): o","line":1,"col":1,"hint":"The character(s) o do not match any rule alternative active at\nthis position.","source_line":"openapi: 3.0.0","report":"[tabnas/unexpected]: unexpected character(s): o\n  --> bookshelf-openapi.yaml:1:1\n  1 | openapi: 3.0.0\n      ^ unexpected character(s): o\n  2 | info:\n  3 |   title: Bookshelf demo API\n\n  The character(s) o do not match any rule alternative active at\n  this position.\n\n  --internal: tag=-; rule=val~o; token=#BD~unexpected; plugins=--"}}
1

The format list gives every format aless reads, with the extensions that imply each one. A format it has no parser for can still be read with a grammar of your own: Read a format aless does not know.