This function extracts a specified file from a tar archive to a temporary directory, loads it using a provided loading function, and returns the loaded object.
Arguments
- tar_file
Character. Path to the tar archive file.
- file_to_extract
Character. Path of the file to extract from the tar archive (can include directories within the archive).
- load_fun
Either a function or a character string naming a function (possibly with package namespace like "package::function") to load the extracted file. Defaults to load_as.
- ...
Additional arguments passed to the loading function.
Examples
ecokit::load_packages(terra, stringr, fs)
# example tar file containing 3 files
tif_file <- system.file("ex/elev.tif", package = "terra")
rds_file <- fs::file_temp(ext = ".rds")
ecokit::save_as(mtcars, out_path = rds_file)
csv_file <- tempfile(fileext = ".csv")
write.csv(iris, csv_file, row.names = FALSE)
tmp_tar <- fs::file_temp(ext = ".tar")
file_list <- c(tif_file, csv_file, rds_file)
base_names <- basename(file_list)
dirs <- dirname(file_list)
for (i in seq_along(file_list)) {
tar_flag <- ifelse(i == 1, "c", "r")
tar_args <- str_glue(
'tar -{tar_flag}f {shQuote(tmp_tar)} -C {shQuote(dirs[i])} \\
{shQuote(base_names[i])}')
invisible(system(tar_args))
}
# List contents of the tar file
print(system2("tar", c("-tf", tmp_tar), stdout = TRUE))
#> [1] "elev.tif" "file272b4820ee63.csv" "file272b646eaaa6.rds"
# example SpatRaster
load_tar_file(
tar_file = tmp_tar, file_to_extract = "elev.tif",
load_fun = "terra::rast")
#> class : SpatRaster
#> size : 90, 95, 1 (nrow, ncol, nlyr)
#> resolution : 0.008333333, 0.008333333 (x, y)
#> extent : 5.741667, 6.533333, 49.44167, 50.19167 (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (EPSG:4326)
#> source : elev.tif
#> name : elevation
#> min value : 141
#> max value : 547
# example CSV file using readr
load_tar_file(
tar_file = tmp_tar, file_to_extract = basename(csv_file),
load_fun = "read.csv") %>%
head()
#> Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#> 1 5.1 3.5 1.4 0.2 setosa
#> 2 4.9 3.0 1.4 0.2 setosa
#> 3 4.7 3.2 1.3 0.2 setosa
#> 4 4.6 3.1 1.5 0.2 setosa
#> 5 5.0 3.6 1.4 0.2 setosa
#> 6 5.4 3.9 1.7 0.4 setosa
# example rds file
load_tar_file(
tar_file = tmp_tar, file_to_extract = basename(rds_file),
load_fun = readRDS) %>%
head()
#> mpg cyl disp hp drat wt qsec vs am gear carb
#> Mazda RX4 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
#> Mazda RX4 Wag 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
#> Datsun 710 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
#> Hornet 4 Drive 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
#> Hornet Sportabout 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
#> Valiant 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1