Linux漏斗家族&管道

Posted 2020-12-28 fqh202

漏斗家族

输出重定向

将正确的命令结果输入到文件中。

须知：echo -- display a line of text

>>

追加重定向，追加到最后一行。

[[email protected] fangqihan]# cat 1.txt 
haha
[[email protected] fangqihan]# echo 'hello linux' >> 1.txt 
[[email protected] fangqihan]# cat 1.txt 
haha
hello linux

2>>

只将错误的命令结果输入到文件中

[[email protected] fangqihan]# asas 'wewe' >> 1.txt 
-bash: asas: 未找到命令
[[email protected] fangqihan]# cat 1.txt 
haha
hello linux
[[email protected] fangqihan]# asas 'wewe' 2>> 1.txt 
[[email protected] fangqihan]# cat 1.txt 
haha
hello linux
-bash: asas: 未找到命令

&>>

不论命令正确与否，都将命令返回的结果输入到文件中。

[[email protected] fangqihan]# echo  'wewe' &>> 1.txt 
[[email protected] fangqihan]# cat 1.txt 
haha
hello linux
-bash: asas: 未找到命令
wewe

方法2：

commands >>3.txt 2>>3.txt

>

标准重定向，先清空，再写入内容。

[[email protected] fangqihan]# cat 1.txt 
a
b
c
d
[[email protected] fangqihan]# echo 'hello linux' > 1.txt 
[[email protected] fangqihan]# cat 1.txt 
hello linux

set -C　 　  # 开启防止标准重定向功能，无法覆盖已存在的文件

    [[email protected] fangqihan]# echo 'haha' > 1.txt 
    -bash: 1.txt: 无法覆盖已存在的文件

set +C          # 关闭此功能

输入重定向

须知：tr -- translate or delete characters

<

从文件中获取输入

[[email protected] fangqihan]# cat 1.txt 
haha
hello linux
-bash: asas: 未找到命令
wewe

[[email protected] fangqihan]# tr 'a-z' 'A-Z' < 1.txt 
HAHA
HELLO LINUX
-BASH: ASAS: 未找到命令
WEWE

<<

<<：here document此处生成文档，cat >> 1.txt << EOF 追加多行。

[[email protected] ~]# cat 1.txt 
huck
END
[[email protected] ~]# cat >> 1.txt << EOF
> a
> b
> c
> EOF
[[email protected] ~]# cat 1.txt 
huck
END
a
b
c
[[email protected] ~]# 

---

管道 |

将管道前的命令的输出 当做 后一个命令的输入。

# example 1：对给定的字符串进行小写转换成大写字母
[[email protected] ~]# echo hello linux |tr a-z A-Z 
HELLO LINUX

# example 2：取出文件内容并将小写字母转换成大写展示出来
[[email protected] ~]# cat 1.txt 
huck
END
a
b
c
[[email protected] ~]# cat 1.txt | tr a-z A-Z
HUCK
END
A
B
C

# example 3：取出文件中的第3-4行的内容
[[email protected] ~]# cat -n 1.txt 
     1  huck
     2  END
     3  a
     4  b
     5  c
[[email protected] ~]# head -4 1.txt |tail -2
a
b

|tee：read from standard input and write to standard output and files

[[email protected] ~]# echo hi,my name is ham |tee 2.txt
hi,my name is ham