UNIX / Linux: Shell Scripting With mail Command

How do I send e-mails from a shell script including file attachments?

The easiest solution is to send email from within shell scripts is mail command as follows. To send a message to one or more people, mail can be invoked with arguments which are the names of people to whom the mail will be sent:

mail -s 'subject' username
mail -s 'subject' vivek@nixcraft.net.in
mail -s 'Duplicate ip detected' -c vivek@nixcraft.net.in  ipadmin@nixcraft.net.in </var/log/ipscan.log
mail -s 'yum update failed' -c vivek@nixcraft.net.in -b  sysadins@groups.nixcraft.net.in </var/log/yum.log
mail -s 'Disk failure'  vivek@nixcraft.net.in < /tmp/message

Where,

-s 'word1 word2' : Specify subject on command line.
-c : Send carbon copies to list of users.
-b : Send blind carbon copies to list. List should be a comma-separated list of names.
< /path/to/file : Read email body using this /path/to/file.

Method #1: Sending File Attachments

The mail command will not work. You need to use uuencode command to send a binary file called reports.tar.gz:

uuencode reports.tar.gz reports.tar.gz | mail -s "Weekly Reports for $(date)" admin@groups.mgmt.nixcraft.net.i

You can email images or any file using the same format:

uuencode file1.png file1.png | mail -s "Funny" users@groups.nixcraft.net.i

Method #2: File Attachments with mutt Command

The mutt is a MUA (mail user agent) - an email client for text based session. It can be used for reading electronic mail under unix like operating systems, including support color terminals, MIME (attachments), and a threaded sorting mode. You can use mutt command as follows to send email attachments:

mutt -s "Filewall logs" -a /tmp/fw.logs.gz vivek@nixcraft.net.in < /tmp/emailmessage.txt

Tip # 1: Empty Mail Body

To use an empty line as the mail body use special file /dev/null or echo command as follows:

echo | mutt -s 'Subject' -a attachment.tar.gz vivek@nixcraft.net.in
mutt -s 'Subject' -a attachment.tar.gz vivek@nixcraft.net.in </dev/null
mail -s "Disk failed @ $(hostname)" mobilenumber@services.api.nixcraft.net.in </dev/null

Tip #2: Writing Mail Body Using Here documents

The here documents (redirection) tells the shell to read input from the current source (HERE) until a line containg only word (HERE) is seen:

#!/bin/bash
...
....
mail -s "Disk Failed" vivek@nixcraft.net.in<<EOF
NAS server [ mounted at $(hostname) ] is running out of disk space!!!
Current allocation ${_SPACE} @ $(date)
EOF
...
..

Tip # 3: Conditional Mail

Use the if else if and the exit status of a command as follows:

[ $(grep -c -i "hardware error" /var/log/mcelog) -gt 0 ] && { echo "Hardware errors found on $(hostname) @ $(date). See log file for the details /var/log/mcelog." | mail -s "HW Errors" mobilephone@api.nixcraft.net.in ;}

#!/bin/bash
....
.....
# backup dirs using gnu/tar
/usr/bin/tar --exclude "*/proc/*" --exclude "*/dev/*" --exclude '*/cache/*' -zcvf /nas05/backup.tar.gz /var/www/html /home/vivek
 
# send an email if backup failed
if [ $? -ne 0 ]
then
 /usr/bin/mail -s "GNU/TAR Backup Failed" vivek@nixcraft.net.in<<EOF
GNU/Tar backup failed @ $(date) for $(hostname)
EOF
else
 /usr/bin/logger "Backup done"
fi
....
..
# clean up
rm $_filename