diff --git a/knowledge base/grep.md b/knowledge base/grep.md
index 4bf8609..544373e 100644
--- a/knowledge base/grep.md	
+++ b/knowledge base/grep.md	
@@ -12,6 +12,11 @@ grep -R --exclude-dir excluded/dir 'pattern' path/to/search/recursively   # gnu
 
 # show line numbers
 grep -n 'pattern' path/to/search
+
+# parallel execution
+# mind the files with spaces in their name
+find . -type f | parallel -j 100% grep 'pattern'
+find . -type f -print0 | xargs -0 -n 1 -P $(nproc) grep 'pattern'
 ```
 
 ## Grep variants
@@ -38,6 +43,18 @@ You can to this using [`pdftotext`](pdfgrep.md) as shown in this example ([sourc
 find /path -name '*.pdf' -exec sh -c 'pdftotext "{}" - | grep --with-filename --label="{}" --color "your pattern"' ';'
 ```
 
+## Gotchas
+
+- Standard editions of `grep` run in a single thread; use another executor like
+  `parallel` or `xargs` to parallelize grepping multiple files:
+
+  ```shell
+  find . -type f | parallel -j 100% grep 'pattern'
+  find . -type f -print0 | xargs -0 -n 1 -P $(nproc) grep 'pattern'
+  ```
+
+  > mind files with spaces in their name.
+
 ## Further readings
 
 - Answer on [StackOverflow] about [how to search contents of multiple pdf files]
diff --git a/knowledge base/parallel.md b/knowledge base/parallel.md
index c1504b4..9d8018d 100644
--- a/knowledge base/parallel.md	
+++ b/knowledge base/parallel.md	
@@ -4,24 +4,28 @@
 
 ```shell
 # group output (--group)
-# use all cpu threads (--jobs 0 or --jobs 100%)
+# fill up cpu threads (--jobs 100%)
 # use newline as delimiter for the arguments in input
 # simulate and print to output the command that would have been executed
 find . -type f \
 | parallel --group --jobs 0 --delimiter '\n' --dry-run clamscan {}
 
 # get the exit status of all subjobs (--joblog $outfile)
+# use all the threads you can (--jobs 0), hammering the cpu
 find . -type d -name .git -exec dirname "{}" + \
-| parallel --group --jobs 100% --tagstring {/} --joblog - 'git -C {} pull --recurse-submodules'
+| parallel --group --jobs 0 --tagstring {/} --joblog - \
+    'git -C {} pull --recurse-submodules'
 
 # inject istio to all deployments in a namespace in (GNU) parallel
-# aka _I have a death wish_
-kubectl -n ${NAMESPACE:-default} get deployments -o jsonpath='{.items[*].metadata.name}' \
-| parallel --group --jobs 0 'kubectl -n ${NAMESPACE:-default} apply -f <(istioctl kube-inject -f <(kubectl -n ${NAMESPACE:-default} get deployments,services {} -o json))'
+kubectl get deployments -o jsonpath='{.items[*].metadata.name}' \
+| parallel --group --jobs 0 'kubectl -n ${NAMESPACE:-default} apply -f \
+    <(istioctl kube-inject -f \
+        <(kubectl get deployments,services {} -o json))'
 
 # given a list of namespaces get pods and their nodes
 parallel --group --jobs 100% --tag \
-  "kubectl --context $KUBE_CONTEXT --namespace {} get pods --output json | jq -r '.items[] | .metadata.name + \"\t\" + .spec.nodeName' -" \
+  "kubectl --context $KUBE_CONTEXT --namespace {} get pods --output json \
+   | jq -r '.items[] | .metadata.name + \"\t\" + .spec.nodeName' -" \
   ::: "${NAMESPACES}" \
 | column -t
 ```
@@ -35,4 +39,4 @@ parallel --group --jobs 100% --tag \
 [man page]: https://www.gnu.org/software/parallel/man.html
 [tutorial]: https://www.gnu.org/software/parallel/parallel_tutorial.html
 
-[Obtaining exit status values from GNU parallel]: https://stackoverflow.com/questions/6310181/obtaining-exit-status-values-from-gnu-parallel#6789085
+[obtaining exit status values from gnu parallel]: https://stackoverflow.com/questions/6310181/obtaining-exit-status-values-from-gnu-parallel#6789085