AWK Process Continued

AWK Process Continued

1

INPUT

1st routine executed before any

input is read

2nd routine(main input loop);

executed for each input line.

Can have multiple pattern-

action statements

3rd routine executed after all input is read.

2

3

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To master awk programming, its important to understand how lines of text of data are processed.

• Prior to processing any text lines, if a BEGIN pattern statement exists, it will then be executed. Remember, this statement will be executed before any data from files are processed, therefore, it only executes once! Then:
• Read a line of Input
• Compare the line of input to each pattern match specified (Remember: You can specify multiple programs or pattern action statements. Each pattern match is done sequentially as specified.
  • Fore match satisfied, perform the appropriate action.
• Repeat Steps two thru four as long as there is input to process.
• Process the END pattern if one exists.

Since the pattern-actions are performed sequentially, you can process data to a specific format; where it will satisfy subsequent pattern matches.