How do you write if else in Unix?

How do you write an IF ELSE statement in Unix?

Their description with syntax is as follows:

  1. if statement. This block will process if specified condition is true. …
  2. if-else statement. …
  3. if..elif..else..fi statement (Else If ladder) …
  4. if..then..else..if..then..fi..fi..(Nested if) …
  5. Syntax: case in Pattern 1) Statement 1;; Pattern n) Statement n;; esac. …
  6. Example 2:

How do you compare two variables in Unix?

Compare Numbers in Linux Shell Script

  1. num1 -eq num2 check if 1st number is equal to 2nd number.
  2. num1 -ge num2 checks if 1st number is greater than or equal to 2nd number.
  3. num1 -gt num2 checks if 1st number is greater than 2nd number.
  4. num1 -le num2 checks if 1st number is less than or equal to 2nd number.

What is the purpose of in Unix?

Unix is an operating system. It supports multitasking and multi-user functionality. Unix is most widely used in all forms of computing systems such as desktop, laptop, and servers. On Unix, there is a Graphical user interface similar to windows that support easy navigation and support environment.

How do I run a shell script?

Steps to write and execute a script

  1. Open the terminal. Go to the directory where you want to create your script.
  2. Create a file with . sh extension.
  3. Write the script in the file using an editor.
  4. Make the script executable with command chmod +x .
  5. Run the script using ./.

How do I run a bash script?

Make a Bash Script Executable

  1. 1) Create a new text file with a . sh extension. …
  2. 2) Add #!/bin/bash to the top of it. This is necessary for the “make it executable” part.
  3. 3) Add lines that you’d normally type at the command line. …
  4. 4) At the command line, run chmod u+x YourScriptFileName.sh. …
  5. 5) Run it whenever you need!

What is if in bash script?

In bash scripting, as in the real world, ‘if’ is used to ask a question. The ‘if’ command will return a yes or no style answer and you can script the appropriate response. As you may have noticed, I have added a backwards ‘if’ (a ‘fi’) at the end of my statement. This is to close off the ‘if’ argument and is required.

What is $? In Bash?

$? is a special variable in bash that always holds the return/exit code of the last executed command. You can view it in a terminal by running echo $? . Return codes are in the range [0; 255]. A return code of 0 usually means everything is ok.

What is =~?

The =~ operator is a regular expression match operator. This operator is inspired by Perl’s use of the same operator for regular expression matching.

What is in if in Linux?

if is a command in Linux which is used to execute commands based on conditions. The ‘if COMMANDS’ list is executed. If its status is zero, then the ‘then COMMANDS’ list is executed. … The exit status of the entire construct is the exit status of the last command executed, or zero if no condition tested true.

What is in if condition in Linux?

Syntax. This code is just a series of if statements, where each if is part of the else clause of the previous statement. Here statement(s) are executed based on the true condition, if none of the condition is true then else block is executed.

What is Flag in shell script?

2.2. Flags. Using flags is a common way of passing input to a script. When passing input to the script, there’s a flag (usually a single letter) starting with a hyphen (-) before each argument.

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