flink: Create a link to a file

In achubaty/amc: Alex's Miscellaneous Code

Description

Creates a symbolic link (symlink) to a file if possible, possibly falling back to a hard link. Hard links are for files only, and won't work across different physical drives. Symlinks won't work on Windows without admin privileges.

Usage

flink(from, to, symlink = TRUE)

Arguments

from, to	character vectors, containing file names or paths (can alternatively be the path to a single existing directory).
symlink	Logical indicating whether to use symlink (instead of hardlink). Default TRUE.

Note

Use caution with files-backed objects (e.g., rasters). See examples.

Author(s)

Alex Chubaty

See Also

file.link, file.symlink, Sys.readlink

Examples

library(datasets)
library(magrittr)
library(raster)

tmpDir <- file.path(tempdir(), 'symlink-test') %>%
  normalizePath(winslash = '/', mustWork = FALSE)
dir.create(tmpDir)

f0 <- file.path(tmpDir, "file0.csv")
write.csv(iris, f0)

d1 <- file.path(tmpDir, "dir1")
dir.create(d1)
write.csv(iris, file.path(d1, "file1.csv"))

d2 <- file.path(tmpDir, "dir2")
f2 <- file.path(tmpDir, "file2.csv")

## create a link to the the directory; d2 should look like d1
flink(d1, d2)  ## symlink
dir.exists(d2) ## TRUE
identical(d1, Sys.readlink(d2)) ## TRUE
file.exists(file.path(d2, "file1.csv")) ## TRUE

## create link to a file
flink(f0, f2) ## symlink
file.exists(f2) ## TRUE
identical(read.csv(f0), read.csv(f2)) ## TRUE

## deleting the link shouldn't delete the original file
unlink(d2, recursive = TRUE)
file.exists(file.path(d2, "file1.csv")) ## FALSE
file.exists(file.path(d1, "file1.csv")) ## TRUE

unlink(f2)
file.exists(f2) ## FALSE
file.exists(f0) ## TRUE

## using rasters and other file-backed objects
f3 <- system.file("external/test.grd", package = "raster")
r3 <- raster(f3)
f4 <- file.path(tmpDir, "raster4.grd")
flink(f3, f4, FALSE) ## hardlink the grd and gri files
flink(extension(f3, "gri"), extension(f4, "gri"), FALSE)

file.exists(f4) ## TRUE
file.exists(extension(f4, "gri")) ## TRUE
r4 <- raster(f4) ## hardlink

f5 <- file.path(tmpDir, "raster5.grd")
flink(f3, f5, TRUE) ## symlink the grd and gri files
flink(extension(f3, "gri"), extension(f5, "gri"), TRUE)
file.exists(f5) ## TRUE
file.exists(extension(f5, "gri")) ## TRUE
r5 <- raster(f5) ## symlink works
identical(r3, r5) ## TRUE

## cleanup
unlink(tmpDir, recursive = TRUE)

achubaty/amc documentation built on April 6, 2021, 6:56 a.m.