R: Add an argument to a parser.

add_argument {argparser}

R Documentation

Add an argument to a parser.

Description

This function adds an argument to an arg.parser object and returns the modified object.

Usage

add_argument(parser, arg, help, default = NULL, type = NULL, nargs = NULL,
  flag = NULL, short = NULL)

Arguments

`parser`	an `arg.parser` object
`arg`	argument name (use no prefix for positional arguments, `--` or `-` prefix for optional arguments or flags)
`help`	help description for the argument
`default`	default value for the argument [default: NA]
`type`	variable type of the argument (which can be inferred from `default`); assumed to be `character` otherwise
`nargs`	number of argument values (which can be inferred from `default`); set to `Inf` for an indefinite number; an optional argument with an indefinite number of values may need to be followed by another optional argument or flag (e.g. `--`) to separate the indefinite optional argument from possible position arguments
`flag`	whether argument is a flag (and does not consume a value) [default: FALSE]
`short`	short-form for flags and positional arguments; short-forms can be assigned automatically based on the first character of the argument name, unless a conflict arises with an existing short-form; to avoid conflicts, add the argument as early as possible

Details

This function supports multiple arguments in a vector. To ensure that the argument variable type is set correctly, either specify type directly or supply default argument values as a list. Argument names that contain dash - in the stem are converted to _.

Value

an arg.parser object with the argument added

Examples

p <- arg_parser("A text file modifying program")

# Add a positional argument
p <- add_argument(p, "input", help="input file")

# Add an optional argument
p <- add_argument(p, "--output", help="output file", default="output.txt")

# Add a flag
p <- add_argument(p, "--append", help="append to file", flag=TRUE)

# Add multiple arguments together
p <- add_argument(p,
    c("ref", "--date", "--sort"),
    help = c("reference file", "date stamp to use", "sort lines"),
    flag = c(FALSE, FALSE, TRUE))

# Print the help message
print(p)

[Package argparser version 0.4 Index]