title: Sed append file is possibile use $?
body: <p>I have this code:</p>
  
  <pre><code>sed -i -e '$a\
  persist.sys.timezone=Europe/Rome \
  ro.miui.region=IT \
  ro.miui.cust_variant=it \
  ro.product.locale.language=it \
  ro.product.locale.region=IT \
  ro.product.mod_device=$DEVICE_NAME_miuita_global \
  ro.miui.mcc=9998 \
  ro.miui.mnc=9999 \
  net.dns2=8.8.4.4' $BUILDPROP'
  </code></pre>
  
  <p>He works perfectly except this string</p>
  
  <pre><code>ro.product.mod_device=$DEVICE_NAME_miuita_global
  </code></pre>
  
  <p>that remains without changes</p>
  
  <p>generally $DEVICE_NAME call the device name automatically for example if work on cancro </p>
  
  <p><code>ro.product.mod_device=cancro_miuita_global</code></p>
  
  <p>I want to point out that in my code bash the function $DEVICE_NAME is perfect so when I use the sed function, I do not see the variable</p>
  
  <p>How can I solve the problem?</p>