This article is about awk command in Linux with examples. here in this article you will learn about Learn about awk syntax, records, fields, line Separator with examples of awk in Unix/Linux.
Question: how to list files as per their size using awk
Answer: ls -l | awk ‘{print $5,$9|”sort -n”}’
Question If the value in the first field in the filename is equal to 0, THEN the entire line ($0) will be printed to the screen.
Answer awk ‘($1 == 0) {print $0}’ filename
Please see our recommended books to learn AWK Programming in a detailed manner:
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Why awk command is used in Unix or Linux
Awk command in Unix / Linux is a powerful command for processing text. Administrator & developer often need to look for the pattern in the files and then process that text as per there requirement. Awk command comes quite handy for these types of task.
In a nutshell, this is something every body working on Linux should be aware . In this post, I will explain little about awk syntax , records, fields, line Separator and the provide 21 awk command in Linux with examples which is quite useful and it will helpful you understand the overall picture of the awk command. Here are the topics for Unix awk command
a) expression evaluates a value to print, test or pass to a function b) expression assigns a new value to a variable or field c) both (a) and (b) d) none of the mentioned
a) jumps out of the innermost for loop b) jumps out of the innermost while loop c) jumps out of the innermost do-while loop d) all of the mentioned
a) is equivalent to “print $0″ b) prints the entire current record c) both (a) and (b) d) none of the mentioned
a) the word following is the name of variable b) we are referring to a field or column in the current line c) $ sign is used for comment d) none of the mentioned
a) writing expressions next to one another, with no operator b) conditional operator c) relational operator d) matching operator
What is awk fields:
(a)Each input line is split into fields. (b)FS: field separator: default is blanks or tabs (c) $0 is the entire line (d)$1 is the first field, $2 is the second field, …. $NF (e) NF is a built-in variable whose value is set to the number of fields.
What is Awk command Working Methodology
(a)Awk reads the input files one line at a time.Each line is called record and Each record is splits into the field (b) For each line, it matches with given pattern in the given order, if matches performs the corresponding action.
| cat file1|awk ‘pattern { action }’ |
(c) If no pattern matches, no action will be performed. (d) In the above syntax, either search pattern or action are optional, But not both. (e) If the search pattern is not given, then Awk performs the given actions for each line of the input.
| cat file1|awk ‘ { action }’ |
(f)If the action is not given, print all that lines that matches with the given patterns which is the default action. (e)Empty braces with out any action does nothing. It wont perform default printing operation.
Some important function in unix Functions:length function to compute length of a string e.g. { print length, $0}substr(s, m, n) produces the sub-string of s that begins at position m and is at most n characters long.