How to Check if a Directory Exists in a Bash Shell Script

When working with Bash shell scripts, one common task is checking if a specific directory exists. This can be crucial for ensuring that scripts do not fail due to missing directories. Below, we’ll explore various methods to check for the existence of a directory, complete with updated code examples for 2024.

Basic Check for Directory Existence

The simplest way to check if a directory exists is to use the -d test in an if statement. Here’s a basic script that does just that:

#!/bin/bash

DIRECTORY="/home/user/mydir"

if [ -d "$DIRECTORY" ]; then
    echo "Directory exists."
else
    echo "Directory does not exist."
fi

Explanation:

• -d checks if the specified path is a directory.
• The script echoes a message based on the result.

Checking for File Existence

If you want to check if a file exists instead, you can use the -f test:

#!/bin/bash

FILE="/home/user/myfile.txt"

if [ -f "$FILE" ]; then
    echo "File exists."
else
    echo "File does not exist."
fi

Explanation:

• -f checks if the specified path is a regular file.

Using mkdir to Check and Create a Directory

Another approach involves attempting to create the directory with mkdir, which is useful if you want to create the directory if it does not exist:

#!/bin/bash

DIRECTORY="/home/user/tempdir"

mkdir "$DIRECTORY" 2>/dev/null
if [ $? -eq 0 ]; then
    echo "Directory created."
else
    echo "Directory already exists."
fi

Explanation:

• mkdir tries to create the directory, and 2>/dev/null suppresses error messages.
• $? captures the exit status of the last command.

Advanced Directory Checks with find

If you need to check for a directory in subdirectories or want to match a pattern, you can use the find command:

#!/bin/bash

DIRECTORY_NAME="myDirectory"
found=$(find /path/to/search -type d -name "$DIRECTORY_NAME")

if [ -n "$found" ]; then
    echo "Directory found at: $found"
else
    echo "Directory not found."
fi

Explanation:

• find searches for directories matching the specified name.
• -n checks if the variable is non-empty, indicating a successful find.

Checking Multiple Directories

You can also check the existence of multiple directories in a single condition:

#!/bin/bash

DIR1="/home/user/dir1"
DIR2="/home/user/dir2"

if [ -d "$DIR1" ] && [ -d "$DIR2" ]; then
    echo "Both directories exist."
else
    echo "One or both directories do not exist."
fi

Explanation:

• && allows you to combine conditions, checking both directories at once.

Using [[ ... ]] for More Robust Conditions

Using the [[ ... ]] construct provides more features and avoids some pitfalls of the single bracket approach:

#!/bin/bash

DIRECTORY="/home/user/mydir"

if [[ -d "$DIRECTORY" ]]; then
    echo "It's a directory."
else
    echo "It's not a directory."
fi

Explanation:

• [[ ... ]] allows for more complex expressions and is generally safer when dealing with variables.

Check Directory Existence with pushd

For a more elegant way to navigate into a directory if it exists, you can use pushd:

#!/bin/bash

DIRECTORY="/home/user/mydir"

if pushd "$DIRECTORY" > /dev/null 2>&1; then
    echo "Changed to directory: $DIRECTORY"
    popd > /dev/null
else
    echo "Directory does not exist."
fi

Explanation:

• pushd attempts to change the directory and redirects output to suppress messages.
• If it fails, it skips the commands inside the then block.

Checking for the existence of a directory in Bash can be accomplished in several ways, each suited to different scenarios. Whether you need a simple existence check, want to create a directory if it doesn’t exist, or search through subdirectories, the above methods provide robust solutions. As you write your scripts, remember to use appropriate checks based on your needs, and always consider the implications of each approach. Happy scripting!