tempfile returns a vector of character strings which can be used as
names for temporary files.
a non-empty character vector giving the initial part of the name.
a non-empty character vector giving the directory name
a non-empty character vector giving the file extension
The length of the result is the maximum of the lengths of the three arguments; values of shorter arguments are recycled.
The names are very likely to be unique among calls to
in an R session and across simultaneous R sessions (unless
tmpdir is specified). The filenames are guaranteed not to be
currently in use.
The file name is made by concatenating the path given by
pattern string, a random string in hex and
a suffix of
tmpdir will be the directory given by
tempdir(). This will be a subdirectory of the per-session
temporary directory found by the following rule when the R session is
started. The environment variables TMPDIR, TMP and
TEMP are checked in turn and the first found which points to a
writable directory is used:
if none succeeds ‘/tmp’ is used. The path should not contain spaces.
Note that setting any of these environment variables in the R session
has no effect on
tempdir(): the per-session temporary directory
is created before the interpreter is started.
tempfile a character vector giving the names of possible
(temporary) files. Note that no files are generated by
tempdir, the path of the per-session temporary directory.
The value will be an absolute path (unless
tmpdir is set to a
relative path), but it need not be canonical (see
normalizePath) and on macOS usually is not.
R processes forked by functions such as
makeForkCluster in package parallel share a
per-session temporary directory. Further, the ‘guaranteed not
to be currently in use’ applies only at the time of asking, and two
children could ask simultaneously. This is circumvented by ensuring
tempfile calls in different children try different names.
The final component of
tempdir() is created by the POSIX system
mkdtmp, or if this is not available (e.g. on
Windows) a version derived from the source code of GNU
It will be of the form ‘RtmpXXXXXX’ where the last 6 characters
are replaced in a platform-specific way. POSIX only requires that the
replacements be ASCII, which allows
. (so the value may appear
to have a file extension) and regexp metacharacters such as
+. Most commonly the replacements are from the regexp
. has been seen.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
unlink for deleting files.
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