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--- awk:awk_fields [2020/05/04 22:59] – peter
+++ awk:awk_fields [2022/06/13 09:37] (current) – peter
@@ Line 1: / Line 1: @@
 ====== AWK - AWK Fields ======
-Understanding Fields.
 Assuming a file exists with the following contents:
@@ Line 7: / Line 5: @@
 <file>
    Peter     Terence   Roux        45
-   Virginia  Genevive  Roux        45
+   Virginia  Genevieve  Roux        45
    Felix     Devon     Roux         5
    David     Bruce     Stevenson   48
@@ Line 14: / Line 12: @@
 </file>
-Issue the following command:
+----
-<code bash>
+===== Understanding Fields =====
+<code awk>
 awk '{print $1,$2,$3,$4,$5}' test.txt
 </code>
-which will display something like:
+returns:
 <code>
 Peter Terence Roux 45
-Virginia Genevive Roux 45
+Virginia Genevieve Roux 45
 Felix Devon Roux 5
 David Bruce Stevenson 48
@@ Line 31: / Line 31: @@
 </code>
-  * AWK has read each field in the file into the variables $1, $2, $3, etc.
+<WRAP info>
+**NOTE:**  AWK has read each field in the file into the variables $1, $2, $3, etc.
   * Each field is split by a field separator, which by default is a space or comma.
     * As can be seen, it does not matter how many spaces separate each field in the input file.
+  * As AWK reads the input, the entire record is assigned to the variable $0.
+</WRAP>
+----
+===== Display Only Certain Fields =====
+To only print the name and surname, i.e. fields $2 and $4:
+<code awk>
+awk '{print $2,$4}' test.txt
+</code>
+returns:
+<code>
+Peter Roux
+Virginia Roux
+Felix Roux
+David Stevenson
+Bob Smith
+Adam Ridley
+</code>
+The ability to address each field with a unique number allows only specific fields to be output.
 <WRAP info>
-**NOTE:**  As AWK reads the input, the entire record is assigned to the variable $0.
+**NOTE** : Fields can be printed out in any order.  For example:
+<code awk>
+awk '{print $4,$2}' test.txt
+</code>
+returns:
+<code>
+Roux Peter
+Roux Virginia
+Roux Felix
+Stevenson David
+Smith Bob
+Ridley Adam
+</code>
+Notice that the surname is now printed before first name.
 </WRAP>
+----
+===== Display Multi-line Output =====
+To output onto multiple lines:
+<code awk>
+awk '{print $2,$3,$4; print $1, $5}' test.txt
+</code>
+returns:
+<code>
+Peter Terence Roux
+45
+Virginia Genevieve Roux
+45
+Felix Devon Roux
+5
+David Bruce Stevenson
+48
+Bob James Smith
+16
+Adam Winter Ridley
+23
+</code>
+<WRAP info>
+**NOTE:**  The semicolon (;) indicates to write some data to a different line.
+</WRAP>
+This could also be written as the following, which will produce the same results:
+<code awk>
+awk '{print $2,$3,$4} {print $1, $5}' test.txt
+</code>
+<WRAP important>
+**WARNING:**  Although both uses of code produce the same result here, be warned that they can produce different results when used with more advanced AWK options.
+</WRAP>
+----