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shantanuo
Asked: 2011-03-08 05:06:45 +0800 CST

suppress blank emails

  • 772

How do I suppress blank emails? FOr e.g. in the following example, I will like to 

some command | mail -s "tables altered on `hostname`" [email protected]

I get the following message "after" sending the message:

Null message body; hope that's ok

This is not ok. I do not want to send mail if there is no text.

email email-server

5 Answers

  1. Best Answer
    #!/bin/sh  

string=`some command`
len=${#string} 
if [ "$len" -gt "0" ]
   then echo $string | mail -s "tables altered on `hostname`" [email protected]
fi

    This will send the mail only if the output of the command is at least 1 character long, but this may include blanks etc.

    (The solution above works, but is unnecessary. man mail reveals the -E option): 

    some command | mail -E -s "tables altered on `hostname`" [email protected]
    • 15

  2. I use the following:

    $ mail --exec 'set nonullbody' -s Test [email protected]

    Which I found in the GNU mail documentation under the nullbody section.

    • 8

  3. One-liner version of SvenW's answer (the creds should go to him, not me)

    string=`some command`; [ "$len" -gt "0" ] && ( echo $string | mail -s "tables altered on `hostname`" [email protected] )
    • 2

  4. For some implementations of mail the command line switch -E is equivalent to --exec which let's you execute a command. In this case daharon's answer works quite well. You can even shortened it to:

    $ mail -E 'set nonullbody' -s Test [email protected]

    If you want to test this behavior use the echo command with the -n command line switch to suppress the trailing newline.

    This command sends an email:

    $ echo -n "something" | mail -E 'set nonullbody' -s Test [email protected]

    But this command doesn't send an email:

    $ echo -n "" | mail -E 'set nonullbody' -s Test [email protected]
    • 2

  5. example:

    echo -n "" | mail -E -s "Log Message" [email protected]

    explain:

    an empty string has endline character so we have to add -n to exclude in this testing echo \n (cr). But if your body message is not existing hence mail will exit/stop sending.

    sources:

    Why does mail -E let me send empty messages? http://heirloom.sourceforge.net/mailx/mailx.1.html

    • 1