How to Check If File and Folder Already Exists in R

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Checking if a file and folder exists in R

Whether you are reading or writing files via programs in the file system, it is necessary to check if that file already exists. If you don’t put a check in place, it can lead to either a program crash or an error.

Checking if the file exists

Checking if a file exists in R

The most efficient way to check if the file exists is to use the built-in file.exists() method. It accepts a path that can lead to a file or directory and returns TRUE if it is there and FALSE otherwise. You can see all of these in the above figure.

Assume that we have a directory called “newDir”, and in that directory, we have a file called “test.R”.

current stat of the newDir directory

Let’s check programmatically if the test.R file is there in the newDir directory:

file <- "newDir/test.R"

if (file.exists(file)) {
  cat("The file is there", "\n")
} else {
  cat("The file does not exist", "\n")
}

# Output: The file is there

Since the file already exists, as we can see from the above screenshot, the if condition executes.

Let’s consider another scenario where we check for the file name new.R, which we know doesn’t exist inside the newDir folder.

file <- "newDir/new.R"

if (file.exists(file)) {
  cat("The file is there", "\n")
} else {
  cat("The file does not exist", "\n")
}

# Output: The file does not exist

By default, the method searches in the current working directory of RStudio that is currently in use.

To search in other directories, you must provide the complete file path.

Checking multiple files’ existence

The file.exists() function is vectorized, meaning you can pass multiple files at once as a vector, and it will check the existence for each one and return TRUE if it exists and FALSE otherwise.

The output will be a logical vector containing TRUE or FALSE values, and it has the same length as the input.

Let’s assume that in our newDir directory, we removed the test.R file and created three new files and one folder:

newDir has three files and one folder

The above screenshot of the newDir directory shows one folder and three files: one.txt, two.txt, and three.txt.

We will check the existence of these files (which we know exist) non-existent files:

file1 <- "newDir/one.txt"
file2 <- "newDir/five.txt"
file3 <- "newDir/four.txt"
file4 <- "newDir/two.txt"
file5 <- "newDir/three.txt"

output_vec <- file.exists(c(file1, file2, file3, file4, file5))

output_vec

# Output: [1] TRUE FALSE FALSE TRUE TRUE

From the above output, you can see that only the first, fourth, and fifth files exist, and it returns TRUE for that. For non-existent, it returns FALSE.

Symbolic links

The file.exists() function supports symbolic links, and it can resolve it and check for the target’s existence.

file.exists(Sys.readlink("symlink_to_file"))

Checking file readability

If the file exists, you can read it using the read.delim() function.

if (file.exists("newDir/test.R") == 0) {
  data <- read.delim("newDir/test.R")
}

fs package

There is a specific file system package called “fs” that you can use to manage file system tasks. For example, it provides the file_exists() function to check if the file exists.

library(fs)

file1 <- "newDir/one.txt"
file2 <- "newDir/five.txt"
file3 <- "newDir/four.txt"
file4 <- "newDir/two.txt"
file5 <- "newDir/three.txt"

fs::file_exists(c(file1, file2, file3, file4, file5))


# Output:
# newDir/one.txt   newDir/five.txt   newDir/four.txt   newDir/two.txt   newDir/three.txt
#      TRUE             FALSE             FALSE             TRUE             TRUE

file.test()

The file_test() function performs shell-style file tests. It can be used to test for the existence of a file, its type, and the permissions on a file.

library(utils)

file <- "/Users/krunallathiya/Desktop/Code/pythonenv/env/newDir/test.R"

file_test("-f", file)

# Output: [1] TRUE

It returns TRUE because the file is inside the newDir directory.

Let’s check for another file called new.R inside the newDir directory.

Check if another file exists

Using the file_test() function, we can check if a new.R file exists inside the newDir directory.

library(utils)

file <- "/Users/krunallathiya/Desktop/Code/pythonenv/env/newDir/new.R"

file_test("-f", file)

# Output: [1] FALSE

FALSE means that the file does not exist.

Checking if the folder exists

Checking if a folder exists in R

There is a built-in specific function called “dir.exists()” that you can use to check if the directory already exists. It returns only TRUE if the directory exists and FALSE otherwise.

In our “newDir” folder, we have a “folder” directory.

folder inside newDir directory

Let’s check for that:

dir.exists("newDir/folder")

# Output: [1] TRUE

And it returns TRUE. If we check for the non-existent directory, it returns FALSE.

dir.exists("newDir/docs")

# Output: [1] FALSE

file.exists()

The file.exists() function not only checks for files but also checks for directories too. It returns TRUE for existence and FALSE otherwise.

file.exists("newDir/folder")

# Output: [1] TRUE

Multiple directories checking

For checking multiple directories, pass a vector of directories to the file.exists() function.

dir1 <- "newDir/folder"
dir2 <- "newDir/folder2"
dir3 <- "newDir/folder3"


file.exists(dir1, dir2, dir3)

# Output: [1] TRUE FALSE FALSE

That’s all!

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