commandArgs

From R.utils v2.0.0 by Henrik Bengtsson

Extract command-line arguments

Provides access to a copy of the command-line arguments supplied when this Rsession was invoked. This function is backward compatible with commandArgs() of the base package, but adds more features.

Keywords: internal, programming

Usage

commandArgs(trailingOnly=FALSE, asValues=FALSE, defaults=NULL, always=NULL, adhoc=FALSE,
  unique=FALSE, excludeReserved=FALSE, excludeEnvVars=FALSE, os=NULL,
  .args=base::commandArgs(trailingOnly = trailingOnly), ...)

Arguments

trailingOnly: If TRUE, only arguments after --args are returned.
asValues: If TRUE, a named list is returned, where command line arguments of type --foo will be returned as
defaults: A character vector or a named list of default arguments. Any command-line or fixed arguments
always: A character vector or a named list of fixed arguments. These will override default and comman
adhoc: (ignored if asValues=FALSE) If TRUE, then additional coercion of character command-line arguments to more specific data t
unique: If TRUE, the returned set of arguments contains only unique arguments such that no two arguments have the same name. If duplicates exists, it is only the last one that is kept.
excludeReserved: If TRUE, arguments reserved by Rare excluded, otherwise not. Which the reserved arguments are depends on operating system. For details, see Appendix B on "Invoking R" in An Introduc
excludeEnvVars: If TRUE, arguments that assigns environment variable are excluded, otherwise not. As described in R --help, these are arguments of format =.
os: A vector of character strings specifying which set of reserved arguments to be used. Possible values are "unix", "mac"<
args: A named list of arguments.
.args: A character vector of command-line arguments.
...: Passed to commandArgs() of the base package.

Value

If asValue is FALSE, a character vector is returned, which contains the name of the executable and the non-parsed user-supplied arguments.
If asValue is TRUE, a named list containing is returned, which contains the the executable and the parsed user-supplied arguments.
The first returned element is the name of the executable by which Rwas invoked. As far as I am aware, the exact form of this element is platform dependent. It may be the fully qualified name, or simply the last component (or basename) of the application. The returned attribute isReserved is a logical vector specifying if the corresponding command-line argument is a reserved Rargument or not.

Backward compatibility

This function should be fully backward compatible with the same function in the base package.

Coercing to non-character data types

When asValues is TRUE, the command-line arguments are returned as a named list. By default, the values of these arguments are character strings. However, any command-line argument that share name with one of the 'always' or 'default' arguments, then its value is coerced to the corresponding data type (via as). This provides a mechanism for specifying data types other than character strings.

Furthermore, when asValues and adhoc are TRUE, any remaining character string command-line arguments are coerced to more specific data types (via type.convert), if possible.

Examples

######################################################################
# Non-parsed command-line arguments
######################################################################
# Display how this instance of R was invoked.
cmd <- paste(commandArgs(), collapse="")
cat("How R was invoked:
");
cat(cmd, "")

# Get all arguments
args <- commandArgs()
print(args)

# Get only "private" arguments and not the name of the R executable.
args <- commandArgs(excludeReserved=TRUE)[-1]
print(args)

# Assert backward compatibility
args0 <- base::commandArgs()
args <- commandArgs()
stopifnot(all.equal(args, args0, check.attributes=FALSE))


######################################################################
# Parsed command-line arguments
######################################################################
# Get all arguments as a named list, e.g. if R is started as:
#
#   R DATAPATH=../data --args --root="do da" --foo bar --details --a=2
#
# then 'args' below will equal
#
#   list(R=NA, DATAPATH="../data" args=TRUE, root="do da",
#        foo="bar", details=TRUE, a="2")
args <- commandArgs(asValue=TRUE)
str(args)

# Turn arguments into R variables
args <- commandArgs(asValue=TRUE, excludeReserved=TRUE)[-1]
keys <- attachLocally(args)
cat("Command-line arguments attached to global environment:
");
print(keys);
str(mget(keys, envir=globalenv()))

Documentation reproduced from package R.utils, version 2.0.0, License: LGPL (>= 2.1)

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