getopt
======

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optparse hex sticker

`getopt` is an R package designed to be used with `Rscript` to write
"\#!"-shebang scripts that accept short and long flags/options. Many
users will prefer using instead the package
[optparse](https://github.com/trevorld/r-optparse) which adds extra
features (automatically generated help option and usage, support for
default values, basic positional argument support).

To install the last version released on CRAN use the following command:

    install.packages("getopt")

To install the development version use the following command:

    install.packages("remotes")
    remotes:install_github("trevorld/r-getopt")

example
-------

An example Rscript using `getopt` with R 4.4+ (i.e. support for `%||%`
and `|>`):

    #!/path/to/Rscript
    library('getopt')
    # get options, using the spec as defined by the matrix
    # fmt: skip
    spec <- matrix(c(
      'verbose', 'v', 2, "integer",
      'help'   , 'h', 0, "logical",
      'count'  , 'c', 1, "integer",
      'mean'   , 'm', 1, "double",
      'sd'     , 's', 1, "double"
    ), byrow = TRUE, ncol = 4L)
    opt <- getopt(spec)

    # if help was asked for print a friendly message and exit
    if (isTRUE(opt$help)) {
      getusage(spec) |> cat()
      quit(status = 0)
    }

    # set reasonable defaults for options that were not specified
    opt$mean <- opt$mean %||% 0
    opt$sd <- opt$sd %||% 1
    opt$count <- opt$count %||% 10L
    opt$verbose <- opt$verbose %||% FALSE

    # print some progress messages to stderr, if requested
    if (opt$verbose) write("writing...", stderr())

    # do some operation based on user input
    rnorm(opt$count, mean = opt$mean, sd = opt$sd) |> cat(sep="\n")

An example Rscript using `getopt` for old versions of R:

    #!/path/to/Rscript
    library('getopt')
    # get options, using the spec as defined by the matrix
    spec <- matrix(c(
      'verbose', 'v', 2, "integer",
      'help'   , 'h', 0, "logical",
      'count'  , 'c', 1, "integer",
      'mean'   , 'm', 1, "double",
      'sd'     , 's', 1, "double"
    ), byrow = TRUE, ncol = 4L)
    opt <- getopt(spec)

    # if help was asked for print a friendly message and exit
    if (!is.null(opt$help)) {
      cat(getusage(spec))
      quit(status = 0)
    }

    # set reasonable defaults for options that were not specified
    if (is.null(opt$mean)) opt$mean <- 0
    if (is.null(opt$sd)) opt$sd <- 1
    if (is.null(opt$count)) opt$count <- 10L
    if (is.null(opt$verbose)) opt$verbose <- FALSE

    # print some progress messages to stderr, if requested
    if (opt$verbose) write("writing...", stderr())

    # do some operation based on user input
    cat(rnorm(opt$count, mean = opt$mean, sd = opt$sd), sep = "\n")
