Let zsteg install script add rubygems PATH to (bash|zsh)rc, config.fish

zsteg/install

@@ -1,3 +1,27 @@
 #!/bin/bash -ex
 
 gem install --user-install zsteg
+
+GEM_BIN_PATH=$(gem environment | grep "USER INSTALL" | awk -F ': ' '{ print $2 }')/bin
+
+MAGIC="# ctf-tools: gem install"
+for f in ~/.bashrc ~/.zshrc; do
+    if [[ -e "$f" ]]; then
+        if ! grep "$MAGIC" "$f" >/dev/null 2>&1; then
+            cat >> "$f" << EOF
+$MAGIC
+export PATH=\$PATH:$GEM_BIN_PATH
+EOF
+        fi
+    fi
+done
+
+f=~/.config/fish/config.fish
+if [[ -e "$f" ]]; then
+    if ! grep "$MAGIC" "$f" >/dev/null 2>&1; then
+        cat >> "$f" << EOF
+$MAGIC
+set -x PATH \$PATH $GEM_BIN_PATH
+EOF
+    fi
+fi