R: Find Full Paths to Executables

Sys.which {base} | R Documentation

## Find Full Paths to Executables

### Description

This is an interface to the system command `which`, or to an emulation on Windows.

### Usage

    Sys.which(names)

### Arguments

`names` | Character vector of names or paths of possible executables.

### Details

The system command `which` reports on the full path names of an executable (including an executable script) as would be executed by a shell, accepting either absolute paths or looking on the path.

On Windows an ‘executable’ is a file with extension ‘.exe’, ‘.com’, ‘.cmd’ or ‘.bat’. Such files need not actually be executable, but they are what `system` tries.

On a Unix-alike the full path to `which` (usually ‘/usr/bin/which’) is found when R is installed.

### Value

A character vector of the same length as `names`, named by `names`. The elements are either the full path to the executable or some indication that no executable of that name was found. Typically the indication is `""`, but this does depend on the OS (and the known exceptions are changed to `""`). Missing values in `names` have missing return values (as from R 3.0.0).

On Windows the paths will be short paths (8+3 components, no spaces) with `\` as the path delimiter.

### Note

Except on Windows this calls the system command `which`: since that is not part of e.g. the POSIX standards, exactly what it does is OS-dependent. It will usually do tilde-expansion and it may make use of `csh` aliases.

In R 2.x.y, arguments containing spaces or other metacharacters needed to be escaped as they would be for a shell: for example Windows paths containing spaces needed to be enclosed in double quotes.

### Examples

    ## the first two are likely to exist everywhere
    ## texi2dvi exists on most Unix-alikes and under MiKTeX
    Sys.which(c("ftp", "ping", "texi2dvi", "this-does-not-exist"))

[Package base version 3.1.2 Index]