The Linux pipeline command is "|", which is used to connect multiple instructions. The output stream of the previous instruction will be used as the operation object of the subsequent instruction. The command format is "Instruction 1 | Instruction 2 | ...", the following instruction of this command must be able to receive the standard input stream command before it can be executed. The pipeline command can only process the correct output of the previous instruction, but cannot handle the error output; the subsequent instruction of the pipeline command must be able to receive the standard input stream command before it can be executed.
#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.
What is the Linux pipe command?
1. The Linux pipeline command is “ | ”, which is used to connect multiple instructions. The output stream of the previous instruction will be used as the following The operation object of an instruction has the command format of "Instruction 1 | Instruction 2 | ...". The subsequent instruction of this command must be able to receive the standard input stream command before it can be executed.
2. The operator of the pipeline command is: "|", which can only process the correct output information sent by the previous instruction, and has no direct processing capability for error information. Then, it is passed to the next instruction as the operation object.
Basic format: Command 1 | Command 2 | …
[Reminder]:
1. The pipeline command can only process the correct output of the previous instruction, but cannot handle the error output;
2. The next instruction of the pipeline command must be able to receive the standard input stream The command can be executed.
Cut— Extract from the command result corresponding content
Step one: Intercept Specify the first 2 lines in the file The 5 character
Command | Meaning |
---|
cut action file | Intercept content from the specified file |
Parameters | English | Meaning |
---|
- c | characters | Select content by characters |
Order:
head -2 file name | cut -c 5
The second step: Intercept Specify the first 2## in the file #The lines are separated by ":"#1,2Section content
Parameters
| English
| Meaning
|
##-d 'Delimiter' | delimiter
| #Specify delimiter
|
-f n1,n2 | ##fifields
Which paragraph of content will be displayed after splitting | , Use , to split |
##Range Control
Meaning | |
nDisplay only the nth item | n- |
Display from the nth item to the end of the line | n-m |
Display items from n to m (including m) | |
Command:
head -2 file name | cut -d ':' -f 1,2
## or
head -2
File name | cut -d ':' -f 1-2 Step Three
: Interception Export the first 2 lines in the specified ## file with ":"#1,2,3Section contentCommand:
head -2 file name | cut -d ':' -f 1 ,2,3
or ##head -2 file name | cut -d ':' -f 1-3
sort—Can sort the contents of text files in units of lines
First step
:
YesString##SortCommand: sort
File name
Step 2
:
DeduplicationSort Its function is very simple, it is to remove duplicates in the output rows OK.
Meaning
| -u | unique |
Remove duplicatesCommand: sort -u File name
Step Three: Sort the values Parameters | English | Meaning |
---|
##-n | numeric-sort | Sort by numerical value | -r | reverse | Reverse the number of times |
Default sorting is based on string: sort file name Ascending order: sort -n file name Descending order: sort -n -r file name Merge: sort -nr File name —> The effect is the same as descending order Step 4: Sort results Parameter | English | Meaning | -t | fifield -separator
| Specify the field separator | -k | key | Sort according to one column |
#
Display all contents in reverse order based on the second section score sort -t ' ' -k2nr
File name Note:
'
'
middle
There is a space
##wc command - display/statistics of the specified number of bytes, number of words, and number of lines in the file InformationStep 1: Display the number of bytes in the specified file , Word count, Line count information. ##CommandMeaning | | ##wc file namedisplaynumber of lines , number of words, number of bytes, specified file information | | Command: wc File name##Step 2
: Only display the number of lines in the file##Parameters EnglishMeaning | | -c | bytesNumber of bytes | - w | words | number of words | -l | lines | number of lines | | Command: #wc -l file name -----> Number of lines wc -c file name -----> Number of bytes wc -w file name - ----> Number of words
Step 3: Count the number of lines, words, bytes of multiple files Command: wc File 1 File 2 File 3 File 4 Example: wc 1.txt 2. txt 3.txt 4.txt Or: Command: wc *.txt
Step 4: View/etc How many sub-contents are there in the directory Command: ls /etc | wc -l
##uniq— Used to check and delete repeated lines in text files [Deduplication】 is generally used in conjunction with the sort - command.
Step one: Achieve duplicate removal effect CommandEnglish | Meaning | | uniq [parameter] fileunique unique | remove Repeat lines | | Command: cat file name | sort | uniq —》Sort according to string And remove duplicates
The second step: not only remove duplicates, but also count the number of occurrences ParametersEnglish | Meaning | | ##-ccount | Count the number of occurrences of each line | | Command: cat file name | sort | uniq -c tee — Put the command result through the pipeline Output to Multiple files 中##CommandMeaning | | Command result| tee file 1 file 2 file 3pass |
tee
You can convert the command results
Through pipe
Output to
Multiple files
middle
- Put the results of deduplication statistics into a.txt,b.txt、c.txt In the file
Command: cat to remove duplicate file names | sort | uniq -c | tee a.txt b.txt c.txt
tr — is used for to replace or Remove characters in the file The first step: Achieving the replacement effect Command | English | Meaning |
---|
Command result | tr replaced character new character | translate | Realize the effect of replacement |
#
Lowercase
he
Replace with uppercase HE echo "helloworld" | tr 'he' ''HE #
Bundle
helloworld
Convert to uppercase echo "helloworld" | tr '[a-z]' 'A-Z' #
Bundle
HELLO
Convert to lowercase echo "HELLO" | tr 'A-Z' 'a-z'
Second step: Achieving the deletion effect Command | English | Meaning |
---|
Command result
| tr -d
Deleted characters
| delete
| #Delete the specified characters
|
# delete
abc1d4e5f
Numbers in ##echo 'abc1d4ee5f' | tr -d '[0-9]'
Step Three: Word count #
Count the number of occurrences of each word Sample data: ##[root@node001 opt]
# cat words.txt hello,world,hadoop
hive,sqoop,flume,hello
kitty,tom,jerry,world
hadoop
Implementation steps:
1
、Change the delimiter
“,”
Replace with newline character
2
, Sort
3
, remove duplicates
4
、Count
# Order
cat words.txt |tr ',' '\n'|sort |uniq -c
can be achieved by - tr [option] character 1 character 2 Replace and and delete Effect
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