Programming principle:
1. Introduction to Programming
early programming
drive hardware default can not be used;
the need for command communication between different hardware device manufacturers, we need drivers to be translated;
more close and hardware development engineers, to learn "compilation language "; and" assembly language "is limited to manufacturers
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 - translation row line execution shell
compiled - once compiled, all of the implementation language c ++ c # c
program instructions = + data
Object-oriented - focusing on the data programming language
for the process - focusing on the instruction
programming language implementation:
1, the order of execution
2, loop execution --FOR (traverse) while (loop condition) an until (and while the opposite)
3, choose to perform - Case branch * * IF
2, the shell script languages introduction
advantages: call the command os (operating system) of the line to achieve all functions;
disadvantages: no library calls
a shell script This includes: 1, the command * * (very important) 2, variable (global variables, local variables, local variables, parameter passing) 3, logic
shell first words! ! !
! # / bin / bash - defined script interpreter
/ etc / shells --- see the current system to support the shell program
echo $ SHELL - view the current session of the shell program
/ etc / passwd - developed a user supported by default shell program
shell execution:
1.bash command to execute the script
-n see a shell script logic error (Note: the word wrong can be whatever)
-x progressive script execution (easy troubleshooting)
2. Authorizes chmod u + filename.sh X
. 3, variable
environment variables
local variables declare command - define variable type
local variable used in the function local
variable types:
numeric:
1. plastic
2. float
3 0 1 Boolean (true or false) ( true False)
string:
1. Common character strings and
2. array
classification of programming languages:
a strongly typed language: - the value must be defined in order to carry out the processing operation or
a weakly typed language: - programming language may automatically identify the type of variable
* * [Polymorphic data having a plurality of attributes, the properties depend on the final use of the data and its operation]
mass parameter
$ -? A command execution status 0 1-255 correct errors
$ 1 $ 2 $ 3 $ 10 { } - incoming data script command back to space as a delimiter
$ # - the amount of statistical parameters passed $ {$ #} this is the last parameter passing
$ * - indicates all parameter passing, pass all parameters to characters string form of output
$ @ - represents all the mass participation, all the mass participation in the form of a list of output
formats defined variables:
NAME = of VALUE
I did not let you define the variable type the command declare
declare -i integer
declare -a array
variable naming:
1. underlined specify variable names
2. hump nomenclature
4, test file test, to determine the conditions
in the script, we need to make the statement branch; it plainly, they do judge
judge is to use the test command to achieve
using the format :
1.test parameter file
2.[条件语句]
常见的test选项：
比较选项：
-eq等于
-ne不等于
-gt 大于
-ge大于等于
-lt小于
-le小于等于
文件判断选项：
-f -d -L -r -w -x
关联选项：
-o 或
-a 与
！ 非
字符串判断
=
！=
-z 判断字符串长度是否为0
-n和z相反
5、逻辑运算
与 &&：两边的命令，都是真，结果才是真
或 ||：两边的命令，一边为真就是真，同时为假才为假
非 ！=
6、算数运算
let 加法
expr 乘法
$[$1+10]
$(($1/$2))
+ - * / % **