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diff --git a/src/tools/README.md b/src/tools/README.md
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--- a/src/tools/README.md
+++ b/src/tools/README.md
@@ -17,3 +17,4 @@
 - [ffmpeg](./ffmpeg.md)
 - [column](./column.md)
 - [sort](./sort.md)
+- [sed](./sed.md)
diff --git a/src/tools/sed.md b/src/tools/sed.md
new file mode 100644
index 0000000..1746c24
--- /dev/null
+++ b/src/tools/sed.md
@@ -0,0 +1,68 @@
+# sed(1)
+
+```
+sed [opts] [script] [file]
+  opts:
+    -i          edit file in place
+    -i.bk       edit file in place and create backup file
+                (with .bk suffix, can be specified differently)
+    -e SCRIPT   add SCRIPT to commands to be executed
+                (can be specified multiple times)
+    -f FILE     add content of FILE to command to be executed
+
+    --debug     annotate program execution
+```
+
+## Examples
+### Delete lines
+```sh
+# Delete two lines.
+echo -e 'aa\nbb\ncc\ndd' | sed '1d;3d'
+# bb
+# dd
+
+# Delete last ($) line.
+echo -e 'aa\nbb\ncc\ndd' | sed '$d'
+# aa
+# bb
+# cc
+
+# Delete range of lines.
+echo -e 'aa\nbb\ncc\ndd' | sed '1,3d'
+# dd
+```
+
+### Insert lines
+```sh
+# Insert before line.
+echo -e 'aa\nbb' | sed '2iABC'
+# aa
+# ABC
+# bb
+
+# Insert after line.
+echo -e 'aa\nbb' | sed '2aABC'
+# aa
+# bb
+# ABC
+
+# Replace line.
+echo -e 'aa\nbb' | sed '2cABC'
+# aa
+# ABC
+```
+
+### Substitute lines
+```sh
+# Substitute by regex.
+echo -e 'aafooaa\ncc' | sed 's/foo/MOOSE/'
+# aaMOOSEaa
+# cc
+```
+
+### Multiple scripts
+```sh
+echo -e 'foo\nbar' | sed -e 's/foo/FOO/' -e 's/FOO/BAR/'
+# BAR
+# bar
+```