redirection, Piping and TR command details

I. Three kinds of I/O devices

1. Standard input (STDIN) accepts keyboard input
   

   REDIRECT Single-line standard input with <
   

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   redirect Multiple lines of standard input with << stop Word to customize the end symbol

   
   

   
   

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2. Standard output (STDOUT) default output to Terminal

1> file redirection to File

1>>file Append to File

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3. Standard error Output (STDERR) default output to Terminal

2>file Redirect to File

2>>file Append to File

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4. Error output and correct output to the same file

&> redirection

&>> Append to

cmd > Path to Fileout 2>&1

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5.set-c Forbidden overrides can be appended with "|>" to force overrides

Set +C allows overwriting

The 6.tee command allows the stdout to be exported to the terminal and saved to a file.

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Two. The use of TR command detailed

tr [OPTION]...SET1 [Set2]

-C using Set1 's complement set

-D Delete the character set in Set1

-S Delete Duplicates

-T converts the set1 corresponding character to the Set2 corresponding character (the corresponding conversion, without remaining unchanged)

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Three. Points for use of piping

1. Pipeline commands can only accept standard correct output (with "2>&1" to implement error output to pipeline command)
   

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2. Common pipe commands have head tail more less TR

Four. Job

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1. Tr ' A-Z ' A-Z ' >/tmp/issue.out </etc/issue

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2. Echo ' Who ' | Tr ' A-Z ' A-Z ' >/tmp/who.out

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3. Mail-s "Help" root << end

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4. ls/root/| Tr ' \ n '
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When converting to a space, enclose the space in quotation marks

5. cat File | Tr ' + ' |BC

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Be careful not to have extra spaces

6.

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By comparing or viewing the Ascci code table to know the ^m corresponding wildcard character \ r

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7.

8.echo $PATH | Tr ': ' \ n '

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9. cat File | Tr-s ' \ n '

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10.cat File | Tr-s ' \ n ' | Tr ' \ n '

This article is from the "Hello" blog, so be sure to keep this source http://tianzhi.blog.51cto.com/11880607/1833557

redirection, Piping and TR command details