Why I Use Printf Over Echo

While echo is the more widely known command for printing text to standard out, I have found behavior and documentation inconsistencies in its varying implementations¹.

macOS echo man page:

Ubuntu echo man page:

In addition, it’s default behavior can cause unintended results when combined with character sensitive commands like base64. Here are a few use cases where echo has caused some trouble for me.

1. Base64 encoding credentials to put into secret management (Hashicorp Vault, kubernetes, etc.)

   #!/usr/bin/env bash
   
   PASSWORD="supersecretpassword"
   
   # echo output
   echo "${PASSWORD}" | base64
   c3VwZXJzZWNyZXRwYXNzd29yZAo=
   
   # printf output
   printf "${PASSWORD}" | base64
   c3VwZXJzZWNyZXRwYXNzd29yZA==

   Echo appends a newline to the end of your output which will be passed in the output piped to the base64 command and also appear in the base64 encoded output.

2. Doing script output

   Desired output

   one line
   two line
   three line
   four

   #!/usr/bin/env bash
   
   INPUT="one line\ntwo line\nthree line\nfour"
   
   # echo output
   echo "${INPUT}"
   one line\ntwo line\nthree line\nfour
   
   # printf output
   printf "${INPUT}"
   one line
   two line
   three line
   four

   The desired output can be achieved using echo with the -e argument, but as shown in the screenshots above, it’s not always documented.