Overview of Shell and bash

Shell is an interactive command interpreter. Shell is independent of the operating system. This design allows you to flexibly choose the appropriate shell. Shell You can type a command in the command line,After being explained by shell, it is transmitted to the Operating System (kernel) for execution. Shell is a command processor. It is a command that reads and explains your input.Program. Except for a command In addition to the cylinder,Shell is also a programming language.You can write programs (called source programs) that can be interpreted by shell. These source programs can contain Shell Program Design commands.In addition to interpreting commands, shell can also be configured and programmed. Shell has its own language that allows users to write programs and run them in a complex way. ShellProgramming LanguageFeatures of many common programming languages, such For example:Loop and ControlStructure. You can generate Shell programs as complex as other applications.  The following is a summary of Shell functions: Find the command location and execute the associated program; New Value for Shell variables; Execute Command substitution; Process I/O redirection and MPs queue functions; Provides an explanatory programming language interface, including statements such as tests, branches, and loops. Bash is the abbreviation of borne again shell, which is a shell. Bash is used by default in Linux. When you input the bash command in the command line, it is equivalent to entering the bash environment. If it is a bash environment, it is entering a sub-Bash Environment(It is equivalent to opening a sub-process ).