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+# awk(1)
+
+```markdown
+awk [opt] program [input]
+    -F <sepstr>        field separator string (can be regex)
+    program            awk program
+    input              file or stdin if not file given
+```
+
+## Input processing
+
+Input is processed in two stages:
+1. Splitting input into a sequence of `records`.
+   By default split at `newline` character, but can be changed via the
+   builtin `RS` variable.
+2. Splitting a `record` into `fields`. By default strings without `whitespace`,
+   but can be changed via the builtin variable `FS` or command line option
+   `-F`.
+
+Field are accessed as follows:
+- `$0` whole `record`
+- `$1` field one
+- `$2` field two
+- ...
+
+## Program
+
+An `awk` program is composed of pairs of the form:
+```markdown
+pattern { action }
+```
+The program is run against each `record` in the input stream. If a `pattern`
+matches a `record` the corresponding `action` is executed and can access the
+`fields`.
+
+```markdown
+INPUT
+  |
+  v
+record ----> ∀ pattern matched
+  |                   |
+  v                   v
+fields ----> run associated action
+```