diff --git a/knowledge base/sed.md b/knowledge base/sed.md
index 84678e8..0a7321c 100644
--- a/knowledge base/sed.md	
+++ b/knowledge base/sed.md	
@@ -4,11 +4,19 @@
 
 ```sh
 # Delete lines matching "OAM" from a file.
-sed -e '/OAM/d' -i .bash_history
+# Overwrite the source file with the changes.
+sed '/OAM/d' -i .bash_history
 
-# Change fstab entries.
+# Show changed fstab entries.
+# Don't save the changes.
 sed /etc/fstab \
   -e "s|#.*\s*/boot\s*.*|/dev/sda1  /boot  vfat   defaults             0 0|" \
   -e "s|#.*\s*ext4\s*.*|/dev/sda2  /      btrfs  compress-force=zstd  0 0|" \
   -e '/#.*\s*swap\s*.*/d'
 ```
+
+## Further readings
+
+- [GNU SED Online Tester]
+
+[gnu sed online tester]: https://sed.js.org/
diff --git a/knowledge base/terraform.md b/knowledge base/terraform.md
index eac0293..bd13e86 100644
--- a/knowledge base/terraform.md	
+++ b/knowledge base/terraform.md	
@@ -164,14 +164,26 @@ resource "azurerm_key_vault_key" "key" {
 }
 ```
 
+### Export the contents of a tfvars file as shell variables
+
+```sh
+# As normal shell variables.
+eval "export $(sed -E 's/[[:blank:]]*//g' file.tfvars)"
+
+# As TF shell variables (TF_VAR_*).
+eval "export $(sed -E 's/([[:graph:]]+)[[:blank:]]*=[[:blank:]]*([[:graph:]]+)/TF_VAR_\1=\2/' file.tfvars)"
+```
+
 ## Further readings
 
 - [CLI Documentation]
 - [Providers best practices]
 - [Version constraints]
 - [References to Named Values]
+- [Environment Variables]
 
 [cli documentation]: https://www.terraform.io/docs/cli/
+[environment variables]: https://www.terraform.io/cli/config/environment-variables
 [providers best practices]: https://www.terraform.io/language/providers/requirements#best-practices-for-provider-versions
 [references to named values]: https://www.terraform.io/language/expressions/references
 [version constraints]: https://www.terraform.io/language/expressions/version-constraints