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  Linux basic introductory tutorial ---- simple text processing
     
  Add Date : 2016-06-28      
         
         
         
  Introduction

In this section we will introduce these orders tr (note not tar), col, join, paste. This section is actually a continuation of the operation of the pipeline can be achieved on command, so we still will combine the pipeline to become familiar with the use of these commands.

A commonly used text processing commands

Second, text processing commands

1.tr command

tr command can be used to delete a text message some text. Or to be converted.

Use:

tr [option] ... SET1 [SET2]
Commonly used options are:

Option Description
-d Delete set1 and matching characters, note that not the whole word matching is not match a sequence of characters
-s removed in the input text and continuously repeat a specified character set1
Example:

# Delete "hello abcabcabc" all the 'o', 'l', 'h'
$ Echo 'hello abcabcabc' | tr -d 'olh'
# Set "hello" in ll, to a weight of l
$ Echo 'hello' | tr -s 'l'
# Input text to all uppercase or lowercase output
$ Cat / etc / passwd | tr '[: lower:]' '[: upper:]'
# The above '[: lower:]' '[: upper:]' You can simply write '[a-z]' '[A-Z]', of course, in turn, will uppercase lowercase variants are possible

More tr use, you can use the --help or man tr obtained.

2.col command

col command may be replaced by peer Tab number of spaces built or reverse this operation.

Use:

col [option]
Commonly used options are:

Option Description
Tab will be converted to spaces -x
-h converting spaces to Tab (default option)
Example:

# Check / etc / protocols are invisible characters, you can see a lot of ^ I, which is actually Tab escape into symbols visible characters
$ Cat -A / etc / protocols
# Col -x will use / etc / protocols in Tab converted to spaces, then use cat to view, you find ^ I missing
$ Cat / etc / protocols | col -x | cat -A

3.join command

Learned about this user databases should not be unfamiliar, this command is used contains two files with the same contents of the line combined.

Use:

join [option] ... file1 file2
Commonly used options are:

Option Description
-t separator specified, the default is spaces
-i ignore case differences
-1 Indicate which field to use the first file to compare the default contrast ,, the first field
-2 Indicate which field to use the second file to compare the default contrast ,, the first field
Example:

# Create two files
$ Echo '1 hello'> file1
$ Echo '1 abcabcabc'> file2
$ Join file1 file2
# The / etc / passwd and / etc / shadow file merge two, in order to specify the ':' as a separator
$ Sudo join -t ':' / etc / passwd / etc / shadow
# The / etc / passwd and / etc / group file merge two, in order to specify the ':' as a separator, respectively, compared to the fourth and three fields
$ Sudo join -t ':' -1 4 / etc / passwd -2 3 / etc / group

4.paste command

paste this command is similar to the join command, which is without comparison data, simply merge multiple files together, separated by Tab.

Use:

paste [option] file ...
Commonly used options are:

Option Description
-d delimiter specifies the merger, the default is Tab
-s do not merge into one line, one line per file
Example:

$ Echo hello> file1
$ Echo abcabcabc> file2
$ Echo www.abcabcabc.com> file3
$ Paste -d ':' file1 file2 file3
$ Paste -s file1 file2 file3

III Summary

These commands are not above all you will often be used, but they are very useful indeed, after the master, you can reduce a lot of work, such as stop with the mouse to copy and paste an assignment in gedit paste inside, the contents of two files merged into a single file, which had only one command to complete.

operation

1, in the "file packing and decompression," an experiment that is mentioned in Windows / dos and Linux / UNIX text file special character inconsistencies, such as line breaks Windows as CR + LF (\ r \ n), Linux / UNIX to LF (\ n). Use cat -A you can see the text contained in the text invisible special characters. Linux, \ n is a $ manifested, and Windows / dos performance as ^ M $, and can be used directly dos2unix unix2dos tool to convert between the two formats, use the file command to view a specific type of file. But now when you do not want to use the two conversion tools, using the previously learned commands manually dos text format to UNIX text format conversion.

2, also remember as a child playing in the top bully small bee game? It should be the name of the Orthodox Space Invaders: Space Invaders.

Use the following command to install, was called ninvaders because this game is based on ncurses graphics library to do command line:

sudo apt-get install ninvaders
     
         
         
         
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