Creating a Directory Only If It Doesn't Exist in KornShell (ksh) on AIX

Creating a Directory Only If It Doesn't Exist in KornShell (ksh) on AIX
Creating a Directory Only If It Doesn't Exist in KornShell (ksh) on AIX

Managing Directory Creation in KornShell Scripts

When writing shell scripts in KornShell (ksh) on AIX, there are scenarios where you need to create a directory only if it doesn't already exist. Using the mkdir command is straightforward, but complications arise if the directory already exists, as this results in an error message.

To avoid the "File exists" error, it's important to implement a check or suppress the error message in your script. This article explores effective methods to ensure your directory creation commands run smoothly without unnecessary errors.

Command Description
-d Used with the test command to check if a directory exists.
mkdir -p Creates a directory and any necessary parent directories, suppressing errors if the directory already exists.
2>/dev/null Redirects standard error to null, effectively suppressing error messages.
$? Represents the exit status of the last executed command.
echo Prints a message to the standard output.
if [ ! -d "directory" ] Conditional statement to check if the specified directory does not exist.

Understanding KornShell Directory Management

The first script checks if a directory does not already exist before attempting to create it. This is done using the if [ ! -d "directory" ] conditional statement, which tests whether the specified directory is not present. If the directory is absent, the script proceeds to create it with the mkdir "directory" command. This method prevents the "File exists" error by ensuring the directory is only created when it is not already there. Additionally, an echo command provides feedback, informing the user whether the directory was created or if it already existed.

The second script takes a different approach by using the mkdir -p command with error suppression. The -p flag ensures that no error is thrown if the directory already exists and also creates any necessary parent directories. By redirecting errors to /dev/null with 2>/dev/null, the script suppresses any error messages that might occur if the directory is already present. This script also checks the exit status of the mkdir command using $? to provide appropriate feedback. If the exit status is zero, it confirms that the directory was created or already existed; otherwise, it indicates a failure.

Creating a Directory Conditionally in KornShell

Shell Script Using KornShell (ksh) on AIX

# Check if the directory does not exist, then create it
if [ ! -d "$DIRECTORY" ]; then
  mkdir "$DIRECTORY"
  echo "Directory created: $DIRECTORY"
  echo "Directory already exists: $DIRECTORY"

Suppressing Error Messages When Creating a Directory

Using mkdir with Error Suppression in KornShell

# Attempt to create the directory and suppress error messages
mkdir -p "$DIRECTORY" 2>/dev/null
if [ $? -eq 0 ]; then
  echo "Directory created or already exists: $DIRECTORY"
  echo "Failed to create directory: $DIRECTORY"

Advanced Techniques for Directory Creation in KornShell

Beyond basic directory creation and error suppression, advanced KornShell (ksh) scripting can offer more robust solutions for managing directories. One such technique involves incorporating logging and notifications into the script. This can be particularly useful in production environments where keeping track of directory creation attempts is essential. By appending log entries to a file, you can maintain a history of all directory operations, which aids in debugging and auditing. This can be achieved by adding echo statements that write to a log file.

Another advanced method is integrating the script with other system monitoring tools. For example, you could use a combination of KornShell and cron jobs to schedule regular checks and ensure necessary directories exist at all times. If a directory is found missing, the script can create it and notify administrators via email. This proactive approach helps in maintaining the system's health and ensures that required directories are always available for critical applications.

Frequently Asked Questions About Directory Management in KornShell

  1. How can I check if a directory exists in KornShell?
  2. Use the if [ -d "directory" ] command to check if a directory exists.
  3. What does the -p flag do in the mkdir command?
  4. The -p flag creates the directory along with any necessary parent directories and does not throw an error if the directory already exists.
  5. How can I suppress error messages from the mkdir command?
  6. Redirect the error output to /dev/null using 2>/dev/null.
  7. What is the purpose of checking $? after a command?
  8. It checks the exit status of the last executed command, with 0 indicating success.
  9. How can I log directory creation attempts?
  10. Use echo statements to append messages to a log file, providing a history of operations.
  11. Can I schedule regular directory checks in KornShell?
  12. Yes, use cron jobs to schedule scripts that check and create directories as needed.
  13. How can I send notifications if a directory is created?
  14. Integrate the script with the mail command to send email notifications upon directory creation.
  15. Is it possible to create multiple directories at once?
  16. Yes, use mkdir -p "dir1/dir2/dir3" to create nested directories in one command.

Final Thoughts on Directory Creation

Effectively managing directory creation in KornShell scripts involves checking for existing directories or suppressing errors when they already exist. By using conditional statements or the mkdir -p command, you can streamline your scripts and prevent unnecessary error messages. Advanced techniques such as logging, notifications, and automation with cron jobs enhance the robustness and reliability of your directory management processes, ensuring that your scripts run smoothly and efficiently.