Q&A

How do you write an if-else loop in shell script?

How do you write an if-else loop in shell script?

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 end an if statement in shell script?

2 Answers. Try replacing the last line ( endif ) with fi , which is the correct token to close an if statement. Also, replace ($2 == “both”) with the correct [ $2 == “both” ] . Note the quotes around $2 , the spaces after [ and before ] and the ; before the then .

How do you write if/then statements in bash?

The if statement starts with the if keyword followed by the conditional expression and the then keyword. The statement ends with the fi keyword. If the TEST-COMMAND evaluates to True , the STATEMENTS gets executed. If TEST-COMMAND returns False , nothing happens; the STATEMENTS get ignored.

What is in if condition in shell script?

Just like other programming languages, shell script uses if-else statements to solve problems. If a condition is true, the algorithm performs a certain action; else , it performs something else.

How do we identify which shell A script should use?

Use the following Linux or Unix commands:

1. ps -p $$ – Display your current shell name reliably.
2. echo “$SHELL” – Print the shell for the current user but not necessarily the shell that is running at the movement.

What is done in shell script?

Shell Scripting for loop

• Keywords are for, in, do, done.
• List is a list of variables which are separated by spaces. If list is not mentioned in the for statement, then it takes the positional parameter value that were passed into the shell.
• Varname is any variable assumed by the user.

What is $# in shell script?

$# : This variable contains the number of arguments supplied to the script. $? : The exit status of the last command executed. Most commands return 0 if they were successful and 1 if they were unsuccessful. Comments in shell scripting start with # symbol.

What is the use of echo in shell script?

Echo is a Unix/Linux command tool used for displaying lines of text or string which are passed as arguments on the command line. This is one of the basic command in linux and most commonly used in shell scripts.

How do I pass a parameter to a shell script?

Arguments can be passed to the script when it is executed, by writing them as a space-delimited list following the script file name. Inside the script, the $1 variable references the first argument in the command line, $2 the second argument and so forth. The variable $0 references to the current script.

What is difference between bash and sh?

Basically bash is sh, with more features and better syntax. Most commands work the same, but they are different. Bash (bash) is one of many available (yet the most commonly used) Unix shells. Bash stands for “Bourne Again SHell”,and is a replacement/improvement of the original Bourne shell (sh).

What is an sh file?

A shell script or sh-file is something between a single command and a (not necessarily) small programm. The basic idea is to chain a few shell commands together in a file for ease of use. So whenever you tell the shell to execute that file, it will execute all the specified commands in order.

How do you add an in shell script?

Use the following syntax to calculate the sum of two integers in a shell script:

1. Using expr command with quotes sum=`expr $num1 + $num2`
2. Use expr command inclosed with brackets and start with dollar symbol. sum=$(expr $num1 + $num2)
3. This is my preferred way to directly with the shell. sum=$(($num1 + $num2))

What does IF_THEN_ELSE mean?

If-then-else meaning A high-level programming language statement that compares two or more sets of data and tests the results. If the results are true, the THEN instructions are taken; if not, the ELSE instructions are taken. The following is a BASIC example: 10 if answer = “y” then print “Yes” 20 else print “No”In many languages, THEN is implied.

What is a shell script or shell scripting?

A shell script is a computer program designed to be run by the Unix shell , a command-line interpreter. The various dialects of shell scripts are considered to be scripting languages. Typical operations performed by shell scripts include file manipulation, program execution, and printing text.

What are shell scripts in Unix?

The Bourne Shell (sh): This was one of the first shell programs that came with Unix and is also the most widely used one.

modeled on the C programming language.

The Bourne Again Shell (bash): The bash shell was developed for the GNU project as a replacement for sh.

How do I create a script in Bash?

To create a bash script, enter the following code: #!/bin/bash. #on displays the actual folder name. echo “the folder is ‘pwd'”. #then the rest of the files. echo “The folder which contains files are ‘ls'”. Save this file by pressing CTRL + O with Nano. Give it the name of your command.