Simple shell programs

The use of else if condition is little different in bash than other programming language. Case statement is used as the alternative of if-elseif-else statement. The output of the following script will be same to the previous else if example. Bash script can read input from command line argument like other programming language. Two argument values read by the following script and prints the total number of arguments and the argument values as output. How you can read command line arguments with names is shown in the following script.

Here, two arguments, X and Y are read by this script and print the sum of X and Y. You can easily combine string variables in bash. Like other programming language, bash has no built-in function to cut value from any string data. But you can do the task of substring in another way in bash that is shown in the following script. Here, the value, 6 indicates the starting point from where the substring will start and 5 indicates the length of the substring. You can do the arithmetical operations in bash in different ways.

How you can add two integer numbers in bash using double brackets is shown in the following script. Two integer values will be taken from the user and printed the result of addition. For situations where you have 2 possible outcomes: — whether this or that — the if-else statement comes in handy.

The script below reads the input score and checks whether it is greater than or equal to In scenarios where there are multiple conditions and different outcomes, the if-elif-else statement is used. This statement takes the following format.

For example, we have a script for a lottery that checks if the number entered is either 90 , 60 or You can use the if statement alongside the AND logic operator to execute a task if two conditions are satisfied. When using the OR logic, that is represented by symbol, either one of the conditions needs to be satisfied with the script to give the expected results.

Bash loops allow users to perform a series of tasks until a certain result is achieved. This comes in handy in performing repetitive tasks. The variable counter is initialized to 1. And while the variable is less than or equal to 10 , the value of the counter will be incremented until the condition is satisfied.

Like the while loop , a for loop is used to execute code iteratively. The for loop below iterates through 1 right through 10 and processes their values on the screen. A positional parameter is a special variable that is referenced in the script when values are passed on the shell but cannot be assigned.

From the output, we can see that the first variable that is printed is the name of the shell script, in this case, test. This site uses Akismet to reduce spam. Learn how your comment data is processed. Script 1: Drawing a Special Pattern!

Whenever you need help, Tecmint. If you liked this article, then do subscribe to email alerts for Linux tutorials. If you have any questions or doubts? Related Posts. This is my script. I am a beginner so I just used the old template. It was successful. Place me to the same folder, where a file to be decrypted is present" echo "Enter the Exact File Name with extension and the original filename before the encryption. Please give the decryption code i had tried writing but not working.. Below is the decryption script!

Hello, Actually I tried file encrypt script but when I execute the code it gives me error. Thank you Reply. How to test the commands in this program. I am using eclipse neon for c with Cygwin.

Please provide list of commands executable for this program. SreeSne I guess you'd better use command line to test c files. Skip to content. Sign in Sign up. Instantly share code, notes, and snippets.