网站建设费怎么做分录seo技巧是什么意思

一、echo命令的基本语法

echo 命令 - 显示一行文本

echo [option] [string]

SYNOPSIS(总览)echo[OPTION]... [STRING]...DESCRIPTION(描述)允许在标准输出上显示STRING(s).-n 不输出行尾的换行符.-e 允许对下面列出的加反斜线转义的字符进行解释.-E 禁止对在STRINGs中的那些序列进行解释.--help 显示帮助并退出(须单独运行)--version 输出版本信息并退出(须单独运行)

二、实例说明：

1、在终端显示一行消息

[root@localhost test]# echo 'hello world!'
hello world!

2、打印变量的值

[root@localhost test]# x=123
[root@localhost test]# echo $x
123

3、打印一行带有双引号的文本

[root@localhost test]# echo 'welcome to "beijing"'
welcome to "beijing"

4、打印一行带有单引号的文本

[root@localhost test]# echo "We're good friends."
We're good friends.

5、输出重定向到文件

[root@localhost test]# echo "I'm very good." > an.txt
[root@localhost test]# cat an.txt 
I'm very good.

6、匹配相同的文件

[root@localhost test]# echo *.txt
1.txt 34.txt 55.txt 66.txt ab.txt an.txt etc_file.txt file2_ect.txt ini.txt num.txt

7、显示当前路径下所有的文件夹和文件

[root@localhost test]# echo *
1.txt 34.txt 55.txt 66.txt ab.txt an.txt echo_test.sh eir etc_file.txt file2_ect.txt for_loop.sh ini.txt num.txt start tay test.sh week.en yer

8、创建新行

[root@localhost test]# echo -e "welcome \nto \nbeijing"
welcome 
to 
beijing

9、单词之间创建制表符空格

[root@localhost test]# echo -e "welcome\tto\tbeijing\tshanghai"
welcome	to	beijing	shanghai

10、合并新行和制表符

[root@localhost test]# echo -e "\twelcome\n\tto\n\tbeijing"welcometobeijing

11、创建垂直制表符

[root@localhost test]# echo -e "welcome\vto\vbeijing"
welcometobeijing

12、合并新行和垂直制表符

[root@localhost test]# echo -e "\nwelcome\n\vto\n\vbeijing"welcometobeijing

13、使用回车选项，替换前面相同的字符

[root@localhost test]# echo -e "welcome\rto \nbeijing"
to come
beijing

14、截断文本

[root@localhost test]# echo -e "welcome to bei\cjing"
welcome to bei[root@localhost test]# 

15、退格键

[root@localhost test]# echo -e "welcome \bto \bbeijing"
welcometobeijing

16、shell 脚本中 echo 命令的使用

[root@localhost test]# cat echo_test.sh 
#!/bin/bash
# Echo Command Usage in Script
os_version=$(grep -i "PRETTY_NAME" /etc/os-release  | awk -F'=' '{print $2}' | sed 's/"//g')
no_cpus=$(lscpu  | grep  '^CPU(s):' | awk -F":" '{print $2}' | sed "s/^[ \t]*//")
total_mem=$(grep MemTotal /proc/meminfo | awk -F":" '{print $2}' | sed "s/^[ \t]*//")
echo 'OS Version :' $os_version
echo 'Number of CPUs :' $no_cpus
echo 'Total Memory :' $total_mem[root@localhost test]# ./echo_test.sh 
OS Version : CentOS Linux 7 (Core)
Number of CPUs : 8
Total Memory : 2027676 kB