| 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.
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.
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"))