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Shell is supported over linux, which is opensource. Shell scripting provides the freedom to automate the execution of the linux command along with programming interface. Shell provides typically like file manipulation, program execution filtering the file, timing and delay, file processing. Like most of the scripting language Shell scripting is an interpreted language.

Shell Scripting language

  • Shell Types:

    The most common shells used for scripting are Bash (Bourne Again SHell), which is the default shell on most Linux distributions, and sh (Bourne Shell), which is a basic shell available on Unix systems. Other shells, such as csh (C Shell), tcsh (enhanced C Shell), and zsh (Z Shell), provide additional features and compatibility.

  • Script File Extension:

    Shell scripts typically have the extension ".sh" but it is not mandatory. The extension is used to identify the file as a shell script and make it easier to recognize.

  • Shebang:

    The shebang (#!) is placed at the beginning of a shell script to specify the shell interpreter that should be used to execute the script. For example, #!/bin/bash indicates that the script should be run using the Bash shell.

  • Comments:

    Shell scripts support comments to document the code and improve its readability. Comments start with the "#" symbol and continue until the end of the line. They are ignored by the shell interpreter.

  • Variables:

    Shell scripts use variables to store and manipulate data. Variables are defined without specifying their type and can store text or numerical values. They are referenced using the variable name preceded by the "$" symbol. Variable assignment is done using the "=" operator.

  • Control Structures:

    Shell scripting provides various control structures for flow control, including conditionals (if-else statements, case statements), loops (for, while, until loops), and function definitions. These control structures enable conditional execution, looping, and modularization of code.

  • Input and Output:

    Shell scripts can read input from the user through command-line arguments and standard input. They can also write output to the terminal (standard output) or redirect it to files (standard output or error).

  • Command Substitution:

    Shell scripts allow command substitution, which means that the output of a command can be used as input for another command or assigned to a variable. Command substitution is achieved using the backtick (`) or the dollar sign and parentheses ($(command)).

  • File Operations:

    Shell scripting provides a wide range of file operations, such as creating, copying, moving, and deleting files and directories. It also supports file permissions, file manipulation, and text processing.

  • Environment Variables:

    Shell scripts have access to environment variables, which are predefined variables that contain information about the system environment. Examples of environment variables include PATH (specifies directories to search for executable files), HOME (user's home directory), and USER (current user's username).

  • Error Handling:

    Shell scripts can handle errors and exceptions using conditional statements and exit codes. The exit code of a command or script is stored in the special variable $?. By convention, an exit code of 0 indicates success, and non-zero codes indicate failure.

  • Debugging:

    Shell scripts can be debugged using various techniques, such as echoing variable values, enabling shell debugging mode (-x option), and adding trace statements.


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