created shell dir

shell/AWK.txt

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+AWK
+
+    * searches files for lines that contain certain pattern
+    * performs operation described in AWK body on line with certain
+      pattern.
+    * performs operation described in AWK body on choosen line
+
+
+    * Basic structure
+
+        awk 'program_you_will_write' input-file1 input-file2
+
+        awk 'BEGIN{
+            code_in_BEGIN_section
+        }
+
+        { code_in_main_body_section }
+
+        END{
+            code_in_END_section
+        }' input-file1 input-file2
+
+    * AWK Commands
+
+        * In AWK body bash features doesn't work
+        * Completely new language in AWK body
+            * print
+            * if-else
+            * for loop
+            * ...
+        
+        * Completely new features we can call on specific line (specific text)
+            * NF (number of fields)
+            * NR (number of records)
+            * RS (records separator)
+            * $1,$2,.. (specific fields)
+            * ...