diff --git a/engine/build.sh b/engine/build.sh
index c972ea8..55427ef 100755
--- a/engine/build.sh
+++ b/engine/build.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 echo "* org-publish"
 emacs \
   --load project.el \
diff --git a/engine/clean.sh b/engine/clean.sh
index 93d5c5b..1c7fcb3 100755
--- a/engine/clean.sh
+++ b/engine/clean.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 echo -n "* Clean site cache"
 rm -rf _site
 rm -rf _cache
diff --git a/engine/compresscss.sh b/engine/compresscss.sh
index 24ed64d..763a779 100755
--- a/engine/compresscss.sh
+++ b/engine/compresscss.sh
@@ -1,8 +1,8 @@
 #!/usr/bin/env nix-shell
-#!nix-shell -i zsh
+#!nix-shell -i bash
 #!nix-shell -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz"
 #!nix-shell -p minify
 
 # nix-shell -p nodePackages.clean-css
 
-minify $1 > $2
+minify "$1" > "$2"
diff --git a/engine/deploy.sh b/engine/deploy.sh
index 6610eb4..5f2b727 100755
--- a/engine/deploy.sh
+++ b/engine/deploy.sh
@@ -1,8 +1,8 @@
-#!/usr/bin/env zsh
+#!/usr/bin/env bash
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 rootdir=${0:h}
-echo $rootdir
+echo "$rootdir"
 
 ./engine/clean.sh
 ./engine/build.sh
diff --git a/engine/dup-for-themes.sh b/engine/dup-for-themes.sh
index f82e968..ae10842 100755
--- a/engine/dup-for-themes.sh
+++ b/engine/dup-for-themes.sh
@@ -2,12 +2,12 @@
 #!nix-shell -i zsh
 #!nix-shell -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz"
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 
 webdir="_site"
 
 debug () {
- print -- $* >/dev/null
+ print -- "$@" >/dev/null
 }
 
 if (($#>0)); then
@@ -24,7 +24,7 @@ trans(){
 
 print -- "Duplicate HTML by themes"
 for fic in $filelist; do
-    if echo $fic|egrep -- '-(mk|min|sci|modern).html$'>/dev/null; then
+    if echo $fic|grep -E -- '-(mk|min|sci|modern).html$'>/dev/null; then
         continue
     fi
     print -n -- "$fic "
diff --git a/engine/mkrss.sh b/engine/mkrss.sh
index 7ef49b0..7cf127a 100755
--- a/engine/mkrss.sh
+++ b/engine/mkrss.sh
@@ -2,7 +2,7 @@
 #!nix-shell -i zsh
 #!nix-shell -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz"
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 # Directory
 webdir="_site"
 postsdir="$webdir/posts"
diff --git a/engine/optim-classes.sh b/engine/optim-classes.sh
index 1890b3a..9226cf4 100755
--- a/engine/optim-classes.sh
+++ b/engine/optim-classes.sh
@@ -2,7 +2,7 @@
 #!nix-shell -i zsh
 #!nix-shell -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz"
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 webdir="_site"
 
 retrieve_classes_in_html () {
diff --git a/engine/optim-html.sh b/engine/optim-html.sh
index 2cf608d..37dcd22 100755
--- a/engine/optim-html.sh
+++ b/engine/optim-html.sh
@@ -2,7 +2,7 @@
 #!nix-shell -i zsh
 #!nix-shell -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz"
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 webdir="_site"
 
 debug () {
diff --git a/engine/pre-deploy.sh b/engine/pre-deploy.sh
index 3e3969c..fce54e9 100755
--- a/engine/pre-deploy.sh
+++ b/engine/pre-deploy.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 echo "Optim HTML size"
 ./engine/optim-html.sh
 echo "Gen themes clones"
diff --git a/engine/serve.sh b/engine/serve.sh
index 9699415..0696921 100755
--- a/engine/serve.sh
+++ b/engine/serve.sh
@@ -1,4 +1,4 @@
 #!/usr/bin/env bash
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 cd _site && sws -d --port 3001 .
diff --git a/engine/sign-project.sh b/engine/sign-project.sh
index be7debf..cee23bd 100755
--- a/engine/sign-project.sh
+++ b/engine/sign-project.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 signer=yann@esposito.host
 
 gpg --local-user $signer --output project.el.sig --detach-sign project.el
diff --git a/engine/sync.sh b/engine/sync.sh
index 55f331f..5c60273 100755
--- a/engine/sync.sh
+++ b/engine/sync.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env zsh
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 rootdir=${0:h}
 echo $rootdir
 
diff --git a/engine/update-file-size.sh b/engine/update-file-size.sh
index a2a954c..a2058ab 100755
--- a/engine/update-file-size.sh
+++ b/engine/update-file-size.sh
@@ -2,7 +2,7 @@
 #!nix-shell -i zsh
 #!nix-shell -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz"
 
-cd $(git rev-parse --show-toplevel)
+cd "$(git rev-parse --show-toplevel)" || exit 1
 webdir="_site"
 
 sizeof() {