Add doc for sed(1)

osx/sed.md

@@ -0,0 +1,16 @@
+# sed
+
+> Run replacements based on regular expressions
+
+- replace all occurrences of a string in a file, and print the result
+
+`sed 's/{{find}}/{{replace}}/g' {{filename}}`
+
+- replace all occurrences of a string in a file, and overwrite the file
+  contents
+
+`sed -i '' 's/{{find}}/{{replace}}/g' {{filename}}`
+
+- replace all occurrences of an extended regular expression in a file
+
+`sed -E 's/{{regex}}/{{replace}}/g' {{filename}}`