Possible to add variables in email when sending via Curl?-CodePudding

I am using Curl to send simple email alerts:

curl smtp://mail.example.com --mail-from [email protected] --mail-rcpt \
[email protected] --upload-file email.txt

email.txt content:

From: John <[email protected]>
To: Joe <[email protected]>
Subject: Example email
Date: Wed, 26 Oct 2022 08:45:16    

Welcome to this example email.

Is it possible to have variables inside email.txt (e.g., make the date dynamic date or include bash user who)?

CodePudding user response：

There is a GNU gettext utility called envsubst, which replaces variables on its standard input with their values. For example:

$ export DATE=$(date  '%F %T')
$ echo '$DATE' | envsubst
2022-10-25 13:17:51

Notice that echo '$DATE' prints $DATE, literally, as the variable isn't expanded by the shell due to the single quotes.

To use that for your example, you could set the desired values in the environment:

export FROM='[email protected]'
export TO='[email protected]'
export DATE=$(date  '%F %T')

then update the email to use the variables:

From: John <$FROM>
To: Joe <$TO>
Subject: Example email
Date: $DATE

Welcome to this example email.

and then use envsubst and a process substitution in your command:

curl smtp://mail.example.com \
    --mail-from "$FROM" \
    --mail-rcpt "$TO" \
    --upload-file <(envsubst < email.txt)

where the output of envsubst < email.txt is

From: John <[email protected]>
To: Joe <[email protected]>
Subject: Example email
Date: 2022-10-25 13:23:44

Welcome to this example email.

Instead of process substitution, you could also use a pipeline and the special - file to read from standard input:

envsubst < email.txt \
    | curl smtp://mail.example.com \
        --mail-from "$FROM" \
        --mail-rcpt "$TO" \
        --upload-file -

CodePudding user response：

Maybe it will help you (see man envsubst):

$ cat test.txt
current date is ${CURRENT_DATE}

$ export CURRENT_DATE=$(date); cat test.txt | envsubst | curl bla-bla