How do you write an IF ELSE statement in Unix?
Their description with syntax is as follows:
- if statement. This block will process if specified condition is true. …
- if-else statement. …
- if..elif..else..fi statement (Else If ladder) …
- if..then..else..if..then..fi..fi..(Nested if) …
- Syntax: case in Pattern 1) Statement 1;; Pattern n) Statement n;; esac. …
- Example 2:
How use 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.
How do I write an if statement in bash?
The syntax of an bash if statement
A short explanation of the example: first we check if the file somefile is readable (“if [ -r somefile ]”). If so, we read it into a variable. If not, we check if it actually exists (“elif [ -f somefile ]”).
What is the if statement?
An if statement is a programming conditional statement that, if proved true, performs a function or displays information. … In the example above, if the value of X were equal to any number less than 10, the program displays, “Hello John” when the script is run.
What is E in shell script?
The -e option means “if any pipeline ever ends with a non-zero (‘error’) exit status, terminate the script immediately”. Since grep returns an exit status of 1 when it doesn’t find any match, it can cause -e to terminate the script even when there wasn’t a real “error”.
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.
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 $1 in bash script?
$1 is the first command-line argument passed to the shell script. Also, know as Positional parameters. … $0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1)
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 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
- Open the terminal. Go to the directory where you want to create your script.
- Create a file with . sh extension.
- Write the script in the file using an editor.
- Make the script executable with command chmod +x <fileName>.
- Run the script using ./<fileName>.