suppress blank emails

Question

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`" me@company.com

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.

I am looking for an option within mail command. I do know how to check this using script. — shantanuo, Mar 07 '11 at 13:36

Sven · Accepted Answer · 2011-03-07T13:51:38.847

15

#!/bin/sh  

string=`some command`
len=${#string} 
if [ "$len" -gt "0" ]
   then echo $string | mail -s "tables altered on `hostname`" me@company.com
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`" me@company.com

edited Mar 07 '11 at 13:51

answered Mar 07 '11 at 13:19

Sven

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One liner please? – shantanuo Mar 07 '11 at 13:37
2

See my edit. And read the man page. – Sven Mar 07 '11 at 13:52
mail: invalid option -- E # I get this error message. – shantanuo Mar 08 '11 at 05:07
What OS are you on? There might be many versions of mail(x) available, Linux usually uses the BSD version. Did you check the man page to see if there are other options with that purpose? If there are not, you would need to either use my script of Jeff's reduced version of it. – Sven Mar 08 '11 at 09:36
for Ubuntu: ``some command | mail -e -s "tables altered on `hostname` me@company.com`` – user219901 Mar 31 '17 at 11:01

score 8 · Answer 2 · answered Oct 28 '14 at 09:48

8

I use the following:

$ mail --exec 'set nonullbody' -s Test test@example.com

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

answered Oct 28 '14 at 09:48

daharon

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Ta! ... Cleanest one so far .. Especially when using cron every hour ;) – GerardJP Apr 12 '15 at 08:19

score 2 · Answer 3 · answered Mar 10 '20 at 06:54

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 test@example.com

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 test@example.com

But this command doesn't send an email:

$ echo -n "" | mail -E 'set nonullbody' -s Test test@example.com

score 2 · Answer 4 · answered Mar 07 '11 at 15:50

2

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`" me@company.com )

answered Mar 07 '11 at 15:50

JeffG

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It seems to be missing the assignment of `$len` – Gert van den Berg Jan 12 '17 at 08:51

score 1 · Answer 5 · edited Apr 13 '17 at 12:14

1

example:

echo -n "" | mail -E -s "Log Message" me@mydomain.tld

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

edited Apr 13 '17 at 12:14

Community

1

answered Sep 13 '15 at 14:43

Dung

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You're explanation falls a bit short, mainly because you're not actually answering the original question of how to suppress blank emails. - In my humble opinion you're missing something at the start of your answer along the lines of: *"Many implementations of `mail` support the `-E` command line switch which does `` and an `example of how you would improve the original command line`* and only then your explanation of how even `-E` is not quite foolproof.... – HBruijn Sep 13 '15 at 17:51

suppress blank emails

5 Answers5