Linux awk Command Details

Awk is a powerful text analysis tool, with the search for grep and the editing of SED, which is especially powerful when it comes to analyzing data and generating reports. To put it simply, awk reads the file line-by-row, using spaces as the default delimiter to slice each row, and then perform various analytical processing of the cut.

How to use: awk ' {pattern + action} ' {filenames}

Although the operation can be complex, the syntax is always the same, where pattern represents what AWK looks for in the data, and the action is a series of commands that are executed when a match is found. Curly braces ({}) do not need to always appear in the program, but they are used to group a series of instructions according to a particular pattern. pattern is the regular expression to be represented, surrounded by slashes.

The most basic function of the awk language is to browse and extract information in a file or string based on the specified rules, before awk extracts the information for additional text operations. A complete awk script is typically used to format the information in a text file. Typically, awk is treated as a unit of a file's behavior. awk processes the text by executing the corresponding command for each line that receives the file.

awk built-in variables

ARGC               command-line arguments argv               command-line parameter arrangement environ            support the use of system environment variables in queues filename           awk browses the file name Fnr the                number of records to browse files FS                 Set input field delimiter, equivalent to command line-F option NF                 Browse record number of fields nr                 Read Record count ofs                output field delimiter ors                Output record delimiter Rs                 control record delimiter the $ variable refers to the entire record. $ $ represents the first field of the current row, which is the second field of the current row,...... And so on

$NF is number finally, which represents the last column of information, which is different from the variable NF, the variable NF counts the total of each row

Common Command Display

AWK excels at column output

Search all rows with the root keyword/etc/passwd

Awk  

Search all lines that have the root keyword/etc/passwd and display the corresponding shell

Statistics/etc/passwd: File name, line number per line, number of columns per row, corresponding full line contents:

Awk-  F ': '  {print ' filename: ' filename ', linenumber: ' NR ', columns: ' NF ', linecontent: ' $ '/etc/passwd

Use printf instead of print to make your code more concise and easy to read

Awk-f: ' {printf ("filename:%10s, linenumber:%3s,column:%3s,content:%3f\n", filename,nr,nf,$0)} '/etc/passwd

Print the second line of/etc/passwd/information

Awk-f: ' nr==2{print ' filename: ' filename, $ A} '/etc/passwd

How Awk uses the filter

LS-LF | awk '/^d/'   

Specify a specific delimiter to query the first column

Awk-f ":" ' {print $} '/etc/passwd  

Specify a specific delimiter to query the last column

Specify a specific delimiter, query the second-to-last column

Awk-f ":" ' {print $NF-1} '/etc/passwd  

Gets the information for the first column of row 12th to 31st

Awk-f ":"  

Use of multiple separators:

[[email protected] ftl]# awk-f "[/]" ' NR = = 4 {print $, ' \ n ', ' $ '/etc/passwd here with/as delimiter, multiple separators using [] and then write the delimiter inside

Begin and end are added

[Email protected] ftl]# CAT/ETC/PASSWD | Awk-f: ' begin{print ' name, Shell '} {print $, $NF} end{print ' Hello World  '} '

View the most recently logged on IP information

AWK Programming-- Variables and Assignments

In addition to Awk's built-in variables, awk can also customize variables, and the looping statements in awk also draw on the C language, supporting while, Do/while, for, break, continue, which have the same semantics as the C language.

Count the number and sum of files larger than 100k in a folder

Ls-l|awk ' {if ($5>100) {count++; sum+=$5}} {print "Count:" Count, "sum:" Sum} '  "because awk polls the statistics, the entire process is displayed" Ls-l|awk ' {i F ($5>100) {count++; sum+=$5}} end{print "Count:" Count, "sum:" Sum} ' "The final result is displayed only after the end of the day"

Note:count is a custom variable. The previous action{} is only one print, in fact, print is just a statement, and action{} can have multiple statements, separated by a number;

Statistics show/ETC/PASSWD's account

Awk-f: ' {count++;} End{print count} '/etc/passwd         cat/etc/passwd|wc-lawk-f ': ' BEGIN {count=0;} {Name[count] = $1;count++;}; End{for (i = 0; i < NR; i++) print I, Name[i]} '/etc/passwd

Linux awk Command Details