A Bash Shell Script is a text file that contains a series of commands that can be run multiple times. It is used to automate repetitive processes on the Linux filesystem.
- Open a Bash shell and type the following: if [ -f $file ]; then echo “File exists.” fi
Steps to check File Exists in Linux Bash Scripts
Check If File Exists
Step 2: If the file does not exist, Bash will create it for you. Step 3: To check if a file is in a particular directory, use the “-d” option (for directory) and specify the directory where the file should be checked.
If the user is not logged in, then The user is redirected to the login page. ..
Check File Existence using shorter forms
If you are using Bash, you can check if a file exists or not directly in your shell by running the command “file”.
This file exists on your filesystem and is not writable by the user.
If Bash can’t find the file specified with the “-f” option, it will run the command in parentheses instead.
passwd This will show you the contents of the “/etc/passwd” file if it exists. If it does not exist, it will show you the empty string.
This file exists!
Shorter forms are closely related to exit statuses. ..
When you run a Bash command, it always exits with an error status. Errors range from 0 to 6, and 1 through 6.
If the command on the left returns a nonzero exit status, then the command on the right will not be executed. ..
Checking multiple files
In some cases, you may want to check if multiple files exist on your filesystem and if they are correct.
-f test-files && echo “Files not found.”
Check If File Does Not Exist
If you do not find a file called “file.txt” on your filesystem, you can check if it exists by running the command “file -p”.
Step 1: To check if a file does not exist using Bash, use the “!” symbol followed by the “-f” option and the file you want to check. ..
If you type “file not found” in a terminal, you will get a message that says “file not found.” If you use shorter forms of the command, such as “file not found?” or “file not exist?” these messages will be replaced with the shorter form.
If you want to check if a file exists, you can use the “||” operator. This will return true if the file exists, and false otherwise. ..
This file does not exist!
The “||” operator will execute the command on the right if and only if the command on the left fails. If both commands succeed, then the “&&” operator will be used instead. ..
-f test.txt test.txt does not exist
Check If Directory Exists
Step 2: If the directory does not exist, Bash will create it for you. If the directory exists, Bash will check it for files and directories. If any are found, Bash will print a message indicating that the directory is present and can be used.
#!/bin/bash echo “Is $1 there?” if [ “$1” != "" ]; then echo “Yes, $1 is there.” else echo “No, $1 is not there.” ..
Check Directory Existence using shorter forms
If you are using Bash, you can check if a directory exists or not directly in your shell by running the command “dir”.
If the directory /etc does not exist on your filesystem, then the echo command returns “no such file or directory.”
For example, if you want to check the existence of a directory called " Downloads " in Bash, you would use the following command: -d Downloads Step 2: If Bash finds a directory in the current working directory that matches the given pathname, it will create it and populate it with all of the files and directories in that directory. If Bash does not find a directory or file specified on the command line, it will return an error. For example, if you want to create a new directory called " Downloads " in your current workingdirectory, you would use the following command: -d Downloads
To check if the “/etc” directory exists for example, you would use the following command: ls -l /etc
This directory exists!
sudo apt-get update This command updates the apt package database and installs new packages.
Creating a complete Bash script
If you find yourself checking multiple times per day whether a file (or multiple) exists or not on your filesystem, it might be helpful to have a script that can automate this task.
#!/bin/bash if [[ $1 -eq “-” ]]; then echo “No files found” fi if [[ $2 -eq “.” ]]; then echo “Yes files found” fi
#!/bin/bash echo “Hello, world!” exit 0 ..
If the file exists, then the script will return true. If the file does not exist, then the script will return false. ..
To check a file for changes, first cd to the directory containing the file and then touch it to create a new version. Then, chmod u+x the check_file command so that it can be executed by anyone who wants to use it. Finally, use vi to edit the check_file script so that it can report on the changes made to the file. ..
- Open a new file in your text editor of choice and enter the following: #!/bin/bash
- Save the file as “bin.sh”.
- In your terminal, navigate to the folder where you saved “bin.sh” and type the following: bash bin.sh This will execute your script and open a new window displaying the output of the script. ..
Argument expansion can be used to capture all files provided as arguments. ..
If the file “$FILE” does not exist, then echo “The file does not exist!”
If you’re on a computer in your office, you can call your script and start checking if files exist or not. If you’re on a computer in another room, you can call it and start checking if files exist or not.
Final Words
To check if a file exists in bash scripts, use the test command. This will return a nonzero value if the file exists and a zero value if it does not exist.
The file /etc/pass does not exist!The file /etc/file does not exist!
