Shell Primer Basics

1. Build and run the shell program

What is a shell program? Simply put, a shell program is one that contains several lines

File for Shell or Linux commands.

As with programs written in high-level languages, writing a shell program requires a text editor. such as VI.

In the text editing environment, according to the Shell's syntax rules, enter some shell/linux command line, form a complete

's Program Files.

There are three methods of executing shell program Files

(1) #chmod +x file (in/etc/profile, add export Path=${path}:~/yourpath, you can run directly under the command line, like the normal command)

(2) #sh file

(3) #. File

(4) #source file

When writing a shell, the first line must indicate that the system needs that shell to explain your shell program, such as: #! /bin/bash,

#! /BIN/CSH,/BIN/TCSH, or #!. /bin/pdksh.

Variables in the 2.shell

(1) Common system variables

$ #: The number of command line arguments to save the program

$ ? : Save the return code of the previous command

$0: Save program Name

$ *: to ("$ $ ...") To save all the input command-line arguments in the form

$ @: to ("$" ...) To save all the input command-line arguments in the form

(2) Defining variables

Shell language is an interpretive language of non-type, and it is not necessary to declare variables in advance when programming in C++/java languages. Give a

A variable is actually defined as a variable.

In all shells supported by Linux, you can assign values to variables using the assignment symbol (=).

Such as:

Abc=9 (Bash/pdksh cannot leave spaces on both sides of the equals sign)

Set ABC = 9 (tcsh/csh)

Because the variables of the shell program are of no type, users can use the same variable and store the characters sometimes

Integer.

Such as:

NAME=ABC (Bash/pdksh)

Set name = ABC (TCSH)

After the variable is assigned, simply precede the variable with a $ to reference.

Such as:

Echo $ABC