We generally use following syntax of Awk as a command,
\nawk ‘\/search pattern1\/ { Actions 1} \/search pattern 2\/ { Action 2 } filename<\/p>\n
for example:
\nawk ‘\/$2~aws\/ { print $0 } employee.txt<\/p>\n
Here, if second column in the file is department of employees then output will contain records of all employees whose department is ‘aws’.<\/p>\n
Syntax as programming language:<\/p>\n
awk
\n‘BEGIN { Actions}
\n{ACTION} # Action for every line
\nEND { Actions }’ filename<\/p>\n
Example:
\nawk ‘BEGIN {print “Name\\t Department\\t Salary”;}
\n> {print $1,”\\t”,$2,”\\t”,$3;}
\n> END{print “***end of file***”;
\n> }’ employee.txt<\/p>\n
Note :
\n-Columns are represented as $1,$2,$3,etc and $0 represents whole record.
\n-Awk reads the input file’s one line at a time.
\n-Either search pattern or action are optional, But not both.
\n-Empty braces with out any action does nothing. It wont perform default printing operation.<\/p>\n
Awk built-In variables:<\/strong><\/p>\n Awk comes with eight built-in variables that are widely used in scripts.<\/p>\n -FS : Input field separator variable. Lets understand the use of all these variables with an example :<\/p>\n We know that \/etc\/passwd file contains users’ information in a specific format where each field is record is separated by a newline (\\n) and each field is separated by a colon (:). Created a similar file (here named passwd1) . In my example, passwd1 contains 8 records with 7 fields each.<\/p>\n $ cat \/etc\/passwd1\/<\/p>\n Now just create a file that will contain awk code. I named it ‘awk_variables.awk’.<\/p>\n $ vim awk_variables.awk<\/p>\n
\n-OFS : Output Field Separator Variable.
\n-RS : Record Separator variable.
\n-ORS : Output Record Separator Variable.
\n-NR : Number of Records Variable.
\n-NF : Number of Fields in a record.
\n-FILENAME : Name of the current input file.
\n-FNR : Number of Records relative to the current input file.<\/p>\n![\"awk1\"](\"\/blog\/wp-ttn-blog\/uploads\/2014\/06\/awk1.png\")
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