Shell Scripting Interview Questions and Answers

File Test Operator: These operators are used to test a particular property of a file.

-b operator: This operator check weather a file is a block special file or not. It returns true, if the file is a block special file otherwise false.

-c operator: This operator checks weather a file is a character special file or not. It returns true if it is a character special file otherwise false.

-d operator: This operator checks if the given directory exists or not. If it exits then operators returns true otherwise false.

-e operator: This operator checks weather the given file exits or not. If it exits this operator returns true otherwise false.

-r operator: This operator checks weather the given file has read access or not. If it has read access then it returns true otherwise false.

-w operator: This operator check whether the given file has write access or not. If it has write then it returns true otherwise false.

-x operator: This operator check whether the given file has execute access or not. If it has executed access then it returns true otherwise false.

-s operator: This operator checks the size of the given file. If the size of given file is greater than 0 then it returns true otherwise it false.

In Linux Shell Scripting, there are two types of variable

System variables: Created and maintained by Linux itself. This type of variable defined in CAPITAL LETTERS.

User-defined variables: Created and maintained by the user. This type of variable defined in lower letters. System variables can be used in the script to show any information these variables are holding.

Like few important System variables are:

• BASH — Holds our shell name
• BASH_VERSION — Holds our shell version name
• HOME — Holds home directory path
• OSTYPE — Holds OS type
• USERNAME – Holds username who is currently logged in to the machine

• \” Double quote
• \\ Backslash
• \b Backspace
• \c Produce no further output
• \e Escape
• \n New Line
• \r Carriage Return
• \t Horizontal tab
• \v Vertical Tab

There are totally 9 positional parameters present i.e. from $1 to $9

•  It provides a unique user id and password to the user, so that unknown or unauthorized person should not be able to access it.
• At file level, it provides security by providing read, write & execute permissions for accessing the files.
• Lastly, it provides security using file encryption. This method allows encoding a file in an unreadable format. Even if someone succeeds in opening a file, but they cannot read its contents until and unless it is decrypted