1, Introduction to Programming
drive hardware default can not be used
CPU control hardware, the need for command communication between different hardware device manufacturers, we need drivers to "translate";
more nearly and development engineer, to learn "assembly language "; and" assembly language "is limited by the manufacturers;
the underlying C C ++ assembly language is
now programming:
based on high-level language, as well as ultra-high-level language, better enable programmers to achieve programming
classification of programming languages:
high-level language
ultra high-level language to be translated into computer-readable language (binary instructions)
interpreted - translated line by line execution, the Java Python shell
bash -x filename.sh
compiled --- once compiled, all of the implementation of C language C ++ C # java
program instructions = + data
Object-oriented programming languages --- focus data
for the process to focus on instruction ---
implementation programming language:
1, the order of execution
2 repeatedly executed for (traverse) the while (loop condition) until (while the opposite)
3, --- choose to perform branch if case
2, shell scripting language introduced
advantages: Call os (operating system) command line to achieve all the features.
Cons: no library calls (comparison Python)
shell script include: 1. 2. Command variables (global variables, local variables, local variables, parameter passing) 3 logic
· shell of the first sentence
! # / Bin / bash - - define the script interpreter
/ etc / shells - View current session supported by the system shell program
echo $ SHELL - view the current session of the shell program
/ etc / passwd - developed to support the user's default shell program (/ sbin / nologin)
execute the shell:
1, bash command to execute the script
logic errors -n View shell script
-x progressive display script execution
2, chmod + x filename.sh authorized to
use the full path to the script execution
3, the variable
environment variables
local variables DECLARE: Define variable type
local variable used in the function local
variable types:
numeric:
1. int Integer
2. float a float
3. Boolean 01 (Ture True False False)
string :
1. Common character strings and
2. the array of
classification of programming languages:
a strongly typed language - the value must be defined in order to be processed or operation
weakly typed language - programming language may automatically identify the type of variable
(polymorphic data having a plurality attribute, and the attribute depends on his last used for computing data)
transmitted parameters
$ -? a command execution status 0 1-255 correct errors
$ 1 $ 2 $ .. {10} - command script later break data, a space for the separator
$ # - the number of statistical parameter passing
$ * - indicates all parameter passing, pass all parameters transmitted in the form of a string
$ @ - represents a pass all the parameters, all the parameters passed output in the form of a list of
Defining the variable format:
NAME = value = Assignment == Analyzing
declare type defined parameters
declare -i integer
declare -a array of
variable names:
1. The underlined variable names specify
2. camelCasing embodiment
4, test file test condition is determined
in script, we need to branch statement, you need to test to determine achieved
using the format:
1.test [the option] File
2. [conditionals] before and after the conditional statements spaces!
common test options:
comparison options:
-eq =
-ne
- gt>
-ge> =
-LT-<
-le <=
Analyzing options:
-f determining whether a regular file
-d determines whether the directory file
-L determines whether the connection file
-r -w -x determines whether the read execution file permissions
associated option:
-o or
-a with
! Non-
characters determination:
= determining whether the same string
= not equal!
-Z string is determined whether the presence
-n -z and the opposite
5, logical operations
and - command && sides are true, the result is true
or - || two side edges command is true. The result is true, as well as false, the result is false
non -! =
The logical operators, are there separate command before and after docking
[? $ -Eq 0] && exit 0 || exit 1
6, arithmetic
let 1 + 1
let a =1+1
echo $ a
expr 1+1
let a =1+1
echo $ a
$[$1+10]
a=$[2+3]
echo $ a
$(($1/$2))
a=$((3/2))
echo $ a