How to write the output into the file in Linux

How do I write the output into the file in Linux bash shell? Can you explain I/O redirection for both bash and POSIX shell to write data to the file under Unix or Linux?
[continue reading…]

Bash shell find out if a variable has NULL value OR not

I am a new to shell scripting. How do I check for NULL value in a Linux or Unix shell scripts?
[continue reading…]

How To Bash Shell Find Out If a Variable Is Empty Or Not

My shell script depends upon user input. How do I find out if a variable called $_JAIL path is empty under a Linux / Apple OS X / Unix like operating systems? Can you tell me command on bash shell to find out if a variable is empty?
[continue reading…]

Bash Check If Shell Is Interactive or Not Under Linux / Unix Oses

How do I check in GNU/Bash if a shell is running in interactive mode or not while writing shell scripts?
[continue reading…]

Grep Include Only *.txt File Pattern When Running Recursive Mode

I‘m using Debian Linux as my development workstation. I would like to search a directory called ~/projects/ recursively for “foo” word only for *.txt files. How do I search all text files in ~/projects/ for “foo” word using grep command?
[continue reading…]

Bash Shell: Check If A Function Exists Or Not (Find Out If a Function Is Defined Or Not)

How do I determine if a function called foo() is already defined in a bash script or not? If a function called foo() is defined just call it or show an error message?
[continue reading…]

BASH Shell Test If a File Is Writable or Not

How can you test if a file is writable under UNIX / Linux bash shell scripting and programming language?
[continue reading…]

bash shell scripting