Marco Education July 28 homework

using Linux has been learned just to complete the following jobs 1. Convert the contents of the/etc/issue file to uppercase and save to the /tmp/issue.out file

Think: The general application of TR, plus the output of the pipeline to the file

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2. Convert the current system login user's information to uppercase and save to the /tmp/who.out file

thinking: Ibid .

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3.  a linux root hello, I am  user name ,thesystem version is here,please help me to check it, thanks! operating system version information

thinking: the application of pipelines, Echo within the command WhoAmI and the Cat View command substitution for operating system information; Mail Use of Commands

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The contents of the letter are as follows:

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4. /root/ The list of files, displaying them as a line, separated by a space between the filenames

echo definition description : echo-display a line of text, display text in a single line

without to replace the newline \ n with [: space:] too complex

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The contents of the file are: "1 2 3 4 5 6 7 8 9"   Calculates the sum of all the numbers

thinking: 1 2 3 4 5 6 7 ' are replaced by + , passed to BC man BC understanding BC

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6. Remove the ' ^m ' character from the Windows text file

Think: window and Linux file line of difference is: WinDOS file change behavior carriage return +$,linux file line is only $, through #cat-a filename can view the Windows file ^m, the man document TR, you can see \ r Return

Method One:-D,--delete
Delete characters in SET1, does not translate remove SET1 characters

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Method Two:

-S,--squeeze-repeats
Replace each input sequence of a repeated character, that's listed in SET1 with
A single occurrence of that character
This is simply understood as: match SET1 characters, remove duplicates (continuous and same), and show only one.

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7. Handle the string "Xt.,l 1 jr#! $mn 2 c*/fe 3 uz 4", preserving only the numbers and spaces

Method One:

Thinking:

-C,-C,--complement
Use the complement of SET1 with SET1 complement
-CD that is to delete SET1 the complement set

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Method Two:

Think:-D Delete letters [: Alpha:] and punctuation [:p UNCT:]

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8. Display the PATH variable in a separate row for each directory

Think: simply pipe-pass, replace

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9. Delete blank lines for the specified file

think: Remove duplicates with-s \ n,

considering the need to edit the software, TR cannot make file edits, so reference MV

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Question: If the first line of the file is blank line, the individual did not think of the method. Consider using sed to command sed '/^$/d ' -I FILENAME
to display each word (letter) in a file in a separate line, with no blank lines

thinking: The complement of the-C letter, replaced by \ n, and add-s to heavy

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Question: The same cannot be deleted at the beginning of a blank line. Need to introduce sed command

Marco Education July 28 homework