shell

args - Shell Arguments Appender Middleware

The args middleware appends the values provided under the args key to a shell command about to be executed. This is mostly for convenience and clarity - arguments can also be provided to the command string directly, although this often results in long execution strings that are harder to test and annotate with meaningful comments.

Note the difference between shell arguments (passed to the shell command) and pipe arguments (everything provided in the pipe invocation yaml, including the shell arguments under the args key).

Arguments

The args middleware expects an array of values, each in one of the following formats (mixing formats is fine).

Formats

Plain string

- some_pipeline:
    args:
      - string_argument

Long form options

For convenience, options of the common form --flag and --key=string_value can be provided as

- some_pipeline:
    args:
      - flag: true
      - unused_flag: false
      - key: string_value

This form is applied whenever the key does not start with a - and is not a single letter.

Short form options

If the key is a single letter, it will instead be appended to the shell command as -a (for boolean true value) or -cstring_value (for string value) without a space between key and value.

- some_pipeline:
    args:
      - a: true
      - b: false
      - c: string_value

Explicit form

Keys that start with a - will be appended as is, with the value concatenated.

- some_pipeline:
    args:
      - -a: string_value

results in -astring_value being appended.

This form can be used to enforce some custom formats:

- some_pipeline:
    args:
      - "-a ": string_value
      - "-b=": string_value
      - "--c": string_value
      - "--d ": string_value

results in -a string_value -b=string_value --string_value --d string_value being appended to the shell command.