C function to get mtime of a file, from R

mtime.R

library(inline)
get_mtime <- cfunction(
  signature(filename = "character"),
  includes = "
    #include <time.h>
    #include <sys/stat.h>",
  body = '
    const char* path = CHAR(asChar(filename));
    struct stat attr;
    stat(path, &attr);
    return Rf_ScalarReal(attr.st_mtime);
  '
)

mtime <- get_mtime("DESCRIPTION")
as.POSIXct(mtime, origin = "1970-01-01", tz = "UTC")