From fb719f52b73920fb18c7f3080ebb1fc73300be49 Mon Sep 17 00:00:00 2001
From: johannst <johannes.stoelp@gmail.com>
Date: Tue, 17 Mar 2020 23:48:21 +0100
Subject: added awk

---
 src/SUMMARY.md |  1 +
 src/awk.md     | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 src/awk.md

(limited to 'src')

diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index 7f385d7..fe0b341 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -2,6 +2,7 @@
 
 - [ld.so](./ld.so.md)
 - [git](./git.md)
+- [awk](./awk.md)
 - [gdb](./gdb.md)
 - [radare2](./radare2.md)
 - [emacs](./emacs.md)
diff --git a/src/awk.md b/src/awk.md
new file mode 100644
index 0000000..0186416
--- /dev/null
+++ b/src/awk.md
@@ -0,0 +1,44 @@
+# 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
+```
-- 
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