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Enviar e-mails con adjuntos desde la terminal con sendmail [Bash script]

En varias ocasiones, he necesitado enviar un e-mail a un compañero de trabajo (o a mí mismo) con información recién extraída de un servidor (por ejemplo un CSV de base de datos o información subida desde la web) y lo que he hecho al final ha sido bajármelo por SSH y una vez en mi ordenador he enviado el archivo donde ha sido necesario. Si eres como yo, que siempre tengo una sesión SSH abierta en mi servidor, ganarás un par de minutos con este script.

El siguiente script envía un correo electrónico utilizando sendmail. sendmail no es difícil, simplemente tenemos que escribir como entrada del correo las cabeceras necesarias y el mensaje, aunque podemos echar unos minutos hasta que se puede enviar correctamente el mensaje.
El problema con las cabeceras viene cuando tenemos que enviar archivos adjuntos, ya que las cabeceras que tenemos que enviar son un poco más complejas, y luego tenemos que codificar el archivo para que encaje en un e-mail y es algo que a mano resulta muy pesado.

Pues nada, si salvamos esto como gemail.sh sólo tenemos que hacer lo siguiente:

$ email.sh destino@servidor.com “Asunto del mensaje” “Hola mundo! Te mando un mensaje”

para enviar un mensaje normal, si queremos enviar adjuntos:

$ email.sh destino@servidor.com “Asunto del mensaje” “Hola mundo! Te mando un mensaje” fichero1 fichero2

siempre y cuando existan los archivos, la cosa irá bien, aunque también podemos insertar cabeceras nuevas en el correo, por ejemplo From (para especificar el remitente), CC y BCC (para copias) y Reply-to (para responder a esta dirección), etc. de la siguiente manera:

$ email.sh destino@servidor.com “Asunto del mensaje” “Hola mundo! Te mando un mensaje” “From: Yo mismo ” “CC: un_amigo@direccion.com” fichero1 fichero2…

Siempre y cuando tengamos sendmail configurado, todos los e-mails se enviarán. Si algún e-mail no ha salido, podemos ver en /var/log/mail.log y /var/log/mail.err qué ha pasado con el envío, ya que sendmail se limita a encolar los mensajes, que ya se podrán enviar con el método que tengamos configurado (postfix, nullailer, etc)

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#!/bin/bash

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# gemail.sh  Copyright (C) 2014  Gaspar Fernández <gaspar.fernandez@totaki.com>

# This bash script will help you to use sendmail allowing us to send e-mails from
# the terminal in a friendly way just say destination, subject and body in the command
# arguments. It allows us also to send mail attachments with local files and allows you
# to use internal sendmail application or connection to a SMTP server.
#
# I find it interesting when using remotely a server with SSH and I must send a file
# located in it to someone. I wrote this little script to send the file directly to
# the destination.

# Changelog:
# - 20160902: Fixed bad python indentation (after yesterday's re-indentation)
# - 20160901: Fix selecting SMTP user
#             Fix when sending mails through cron jobs (again) this time,
#             when sending from scripts ran in cron jobs. /dev/stdin is
#             present in some conditions but with no data.
#             Indentation fix
# - 20160706: Several new CLI options.
# - 20160705: Added SMTP support with tiny python script
# - 20160703: Fixes adding headers and autoheaders
# - 20160415: Fix sending mails through cron job. Must check permissions over /dev/stdin
# - 20150216: Allow body to be read from stdin
# - 20150210: Bug fix separate recipient and non-recipient headers (for some reason some
#             mailers didn't do it right when they are mixed.
# - 20150210: Added SENDMAIL_BASIC_ARGS to call sendmail -t and allow more recipients
# - 20150113: Bug fix (sendmail with no arguments)
# - 20141212: Preview mode and additional sendmail find
# - 20141211: Removed extra \n when no extra headers
# - 20141208: Allows us to send many attachments
# - 20141206: Code clean up
# - 20141129: Initial idea of the script and wrote basic functionality

# To do:
#  - Doc and examples !!!

VERSION="0.8"
#MAIL_BOUNDARY="m41lb0und4ry"       # We can randomize it later
MAIL_BOUNDARY=`cat /dev/urandom | tr -dc 'a-zA-Z0-9' | head -c 40`
SENDMAIL_COMMAND=`which sendmail`
# Read recipients from mail (to use CC and so)
SENDMAIL_BASIC_ARGS="-t"
SENDMAIL_COMMAND="";
SMTP_DEFAULT_SECURITY="starttls"
_MYNAME=$0

function showUsage()
{
    # We must extend this help to use headers and so
    if [ -n "$1" ]
    then
        echo "Sorry: $1"
        echo
    fi
    echo "gemail.sh Version $VERSION"
    echo "Sends e-mails from terminal the easy way. (https://github.com/gasparfm/gscripts)"
    echo
    echo "Use:"
    echo "  $_MYNAME [options] [destination] [subject] [body] [attachment1] [attachment2] ... [attachmentN]"
    echo
    echo "or:"
    echo
    echo "  $_MYNAME [options] [destination] [subject] [attachment1] [attachment2] ... [attachmentN] < bodyfile"
    echo
    echo "These are the supported options:"
    echo " -t, --to=destination     : Adds to recipient to the e-mail (if this option is"
    echo "                present you can dismiss [destination] argument)."
    echo " -f, --from=origin    : This is YOUR e-mail."
    echo " -s, --subject=subject    : The subject of your message. (if this option is "
    echo "                present you can dismiss [subject] argument)."
    echo " -b, --body=message   : This is yout message. (if this option is present,"
    echo "                you can dismiss [body] argument)."
    echo " -p, --preview        : Don't send the message, just preview the e-mail."
    echo " -h, --header=content : Adds new header to the e-mail. Allowed headers are:"
    echo "                From, CC, BCC, Reply-to, Date, Organization, "
    echo "                X-Mailer and Message-Id."
    echo " -a, --attach=file    : Attaches this file to the e-mail."
    echo " -e, --smtp=conn_str  : Gives SMTP server or connection string."
    echo "            This connection string can be: "
    echo "              * server hostname or IP"
    echo "              * user:password@server (if user or password has :"
    echo "                 or @ characters they may be escaped.)"
    echo " -u, --smtp-user=user : Sets SMTP server user."
    echo " -w, --smtp-pass=passwd   : Sets SMTP server password."
    echo " -n, --noautoheaders  : Disables gemail.sh automatic headers."
    echo
    echo "You can also insert some more headers after the attachments:"
    echo "  "From: me@email.ext" or "From: Me <me@myself.ext>" to specify my email"
    echo "  "CC: my@email.ext" or "CC: My friend <my@friend.ext>" for carbon copy"
    echo "  "BCC: my@email.ext" or "BCC: My friend <my@friend.ext>" for blind carbon copy"
    echo "  "Reply-to: another@email.com" for a new reply-to address";
    echo "  Another headers accepted: Date, Organization, X-Mailer, Message-Id"
    echo
    echo "You can use the keyword *preview* to print the command to be executed (if you have attached files the output can be large)"
    exit
}

function findSendmail()
{
    # Try to find again sendmail in extra paths not in $PATH
    EXTRAPATHS=("/usr/sbin/" "/sbin/" "/usr/local/sbin/" "$HOME/.local/bin/")

    for p in "${EXTRAPATHS[@]}";
    do
        if [ -x "${p}sendmail" ]
        then
            echo "${p}sendmail"
            return
        fi
    done
}

function test_py()
{
    if [ -z "$(which python)" ]
    then
        echo "Python not found"
        return;
    fi

    python <<EOF
try:
    import smtplib
except ImportError as er:
        print er
EOF

}

function pysmtp()
{
    TO="$1"
    while read line
    do
        echo "$line"
    done | python <(cat <<EOF
import smtplib
import sys
try:
    smtpObj = smtplib.SMTP('$SMTP_SERVER')
    if ('$SMTP_SECURITY' == 'starttls'):
        smtpObj.starttls()
    if ('$SMTP_USER'):
        smtpObj.login('$SMTP_USER', '$SMTP_PASS')
    message = sys.stdin.read()
    _from = message.find('From:')
    fromstr = 'root'
    if _from != -1:
        fromstr = message[_from+5:message.find('\n', _from)]
    smtpObj.sendmail(fromstr.strip(), '$_TO', message)
except Exception as e:
    print e
EOF

    )
}

function callsend()
{
    _TO="$1"
    _PREVIEW=$2
    if (( $_PREVIEW==1 ))
    then
        cat
    elif [ $SENDER = "sendmail" ]
    then
        if [ -z "$SENDMAIL_COMMAND" ];
        then
            echo "No sendmail found in your PATH. Make sure you have it!"
            exit 1;
        fi
        $SENDMAIL_COMMAND $SENDMAIL_BASIC_ARGS "$_TO"
    elif [ $SENDER = "smtp" ]
    then
        PYERR="$(test_py)"
        if [ -n "$PYERR" ]
        then
            echo "Python error: $PYERR"
            exit 1;
        fi
        RESPONSE="$(pysmtp "$TO")"
        if [ -n "$RESPONSE" ]
        then
            echo "Error sending via SMTP: $RESPONSE"
            return 1;
        fi
    fi
}

function add_attachment()
{
    ATTACH="$1"
    ATTACH_MIME=`file --mime-type -b "$ATTACH"`
    ATTACH_NAME=`basename "$ATTACH"`
    ATTACH_BASE64=`base64 "$ATTACH"`
    ATTACHMENTS="$ATTACHMENTS
--$MAIL_BOUNDARY
Content-Type: $ATTACH_MIME; name="
$ATTACH_NAME"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="
$ATTACH_NAME"

$ATTACH_BASE64"

}

function add_header()
{
    HEADERINFO="$1"
    OLDIFS=$IFS
    IFS=":"
    read -a HEADER <<< "$HEADERINFO"
    IFS=$OLDIFS
    case ${HEADER[0]} in
        # Separating headers for some mail systems
        "From" | "Reply-to" | "CC" | "BCC" )
            if [ "${HEADER[0]}" = "From" ] || [ "${HEADER[0]}" = "Reply-to" ]
            then
                RECIPIENTS="$(echo -e "$RECIPIENTS" | grep -v "${HEADER[0]}:")"
            fi

            if [ -z "$RECIPIENTS" ]
            then
                RECIPIENTS=$HEADERINFO
            else
                RECIPIENTS="`echo -e "$RECIPIENTS""\n""$HEADERINFO"`"
            fi
            ;;
        "Date" | "X-Mailer" | "Organization" | "Message-Id" )
            MOREHEADERS="$(echo -e "$MOREHEADERS" | grep -v "${HEADER[0]}:")"
            if [ -z "$MOREHEADERS" ]
            then
                MOREHEADERS=$HEADERINFO
            else
                MOREHEADERS="`echo -e "$MOREHEADERS""\n""$HEADERINFO"`"
            fi
            ;;
        "preview")
            PREVIEW=1
            ;;
        *)
            showUsage "Attachment $HEADERINFO not found"
    esac
}

function add_auto_headers()
{
    if [ "$AUTOHEADERS" = "yes" ]
    then
        if [ -z "$(grep "From:" <<< $RECIPIENTS)" ]
        then
            add_header "From: $(echo `whoami`@`hostname`)"
        fi

        if [ -z "$(grep "Date: " <<< $MOREHEADERS)" ]
        then
            add_header "Date: $(date -R) ($(date +%Z))"
        fi

        if [ -z "$(grep "Message-Id: " <<< $MOREHEADERS)" ]
        then
            _FROM=$(grep "From:" <<< $RECIPIENTS)
            add_header "Message-Id: <"$(uuidgen | awk -F'-' -v date=$(date +%Y%m%d%H%M%S) -v at=$(echo $_FROM | cut -d'@' -f2) '{print $1$2"."date"."$3$4"@"at}')">"
        fi
        if [ -z "$(grep "X-Mailer: " <<< $MOREHEADERS)" ]
        then
            add_header "X-Mailer: gemail.sh Ver. $VERSION"
        fi
    fi
}

function smtp_settings()
{
    STS="$1"

    OLDIFS=$IFS
    IFS=$(echo -e "\n")
    while read user
    do
        read pass
        read server
        break
    done <<< $(sed -r 's/([^\:\@]*(\\:[^\:\@]*)*):([^\@]*(\\@[^\:\@]*)*)@([^\/\:]*)/\1\n\3\n\5/' <<< "$STS");
    if [ -z "$user" ]
    then
        showUsage "Wrong SMTP server string: "$STS""
    fi
    SENDER="smtp"
    if [ -z "$pass" ] && [ -z "$server" ]
    then
        # We only have server
        SMTP_SERVER="$user"
    else
        SMTP_SERVER="$server"
        SMTP_USER="$user"
        SMTP_PASS="$pass"
    fi
    SMTP_SECURITY=$SMTP_DEFAULT_SECURITY
}

# Fill missing headers automatically
AUTOHEADERS="yes"
ATTACHMENTS=""
MOREHEADERS=""
RECIPIENTS=""

# By default, no PREVIEW
PREVIEW=0

# By default, sent by sendmail
SENDER="sendmail"

# Parse input arguments
ARGS=$(getopt -q -o "t:f:s:b:ph:a:e:u:w:n" -l "to:,from:,subject:,body:,preview,header:,attach:,smtp:,smtp-user:,smtp-pass:,noautoheaders" -n "gemail.sh" -- "$@");
if [ $? -ne 0 ];
then
    showUsage "Error parsing arguments"
fi

eval set -- "$ARGS";

while [ $# -gt 0 ]; do
    case "$1" in
        -t|--to)
            TO="$2"
            shift;
            ;;
        -f|--from)
            add_header "From: $2"
            shift;
            ;;
        -s|--subject)
            SUBJECT="$2"
            shift;
            ;;
        -b|--body)
            BODY="$3"
            shift;
            ;;
        -p|--preview)
            PREVIEW=1
            ;;
        -h|--header)
            add_header "$2"
            shift;
            ;;
        -a|--attach)
            add_attachment "$2"
            shift;
            ;;
        -e|--smtp)
            smtp_settings "$2"
            shift;
            ;;
        -u|--smtp-user)
            SMTP_USER="$2"
            shift
            ;;
        -w|--smtp-pass)
            SMTP_PASS="$2"
            shift
            ;;

        -n|--noautoheaders)
            AUTOHEADERS="no"
            ;;
        --)
            shift;
            break;
            ;;
        *)
            echo "Unrecognised option "$1""
            showUsage
    esac
    shift;
done
if [ -n "$1" ] && [ -z "$TO" ]
then
    TO="$1"
    shift
fi

if [ -n "$1" ] && [ -z "$SUBJECT" ]
then
    SUBJECT="$1"
    shift
fi

# If we have data in /dev/stdin pick up the email body from /dev/stdin
# -t 0 : make sure stdin (fd=0) is not a terminal as this program is not
# interactive
if [ -r /dev/stdin ] && [ ! -t 0 ]
then
    BODY=$(cat /dev/stdin)
fi
# If we have no body yet, test the argument. In cron jobs /dev/stdin may
# be detected with no data.
if [ -n "$1" ] && [ -z "$BODY" ]
then
    BODY="$1"
    shift
fi

# Additional sendmail find if not in PATH
if [ -z "$SENDMAIL_COMMAND" ];
then
    SENDMAIL_COMMAND=`findSendmail`
fi

# Fill attachments and additional user headers
while [ $# -gt 0 ]
do
    ATTACH="$1"
    if [ ! -r "$ATTACH" ];
    then
        # Not an attachment, ok but it can be an additional header it will have : let's check it
        add_header "$ATTACH"
    else
        add_attachment "$ATTACH"
    fi
    shift
done

if [ -z "$TO" ]
then
    showUsage "No recipient found."
elif [ -z "$SUBJECT" ]
then
    showUsage "No subject found."
elif [ -z "$BODY" ]
then
    showUsage "No body found."
fi

# echo "TO: $TO"
# echo "SUBJECT: $SUBJECT"
# echo "BODY: $BODY"

add_auto_headers

# Send message
( echo "To: $TO";
    if [ -n "$RECIPIENTS" ]; then
        echo -e "$RECIPIENTS"
    fi
    echo "Subject: $SUBJECT";
    if [ -n "$MOREHEADERS" ]; then
        echo -e "$MOREHEADERS"
    fi
    echo "MIME-Version: 1.0";
    echo "Content-Type: multipart/mixed; boundary="$MAIL_BOUNDARY"";
    echo -e "\n"
    echo "--"$MAIL_BOUNDARY;
    echo "Content-Type: text/plain";
    echo -e "Content-Disposition: inline\n";
    echo "$BODY";
    echo -e "$ATTACHMENTS"
    echo "--"$MAIL_BOUNDARY"--") | callsend $TO $PREVIEW

RESULT=$?
if (( $RESULT==0 ))
then
    echo "Message sent successfully";
else
    echo "Could not send message"
fi

Este código lo encontráis también en mi Github.

Actualización 05/11/2016 : Se ha actualizado el código fuente, para copiar y pegar directamente. Estoy preparando también un post con ejemplos de uso muy ilustrativo que nos puede salvar la vida en más de una ocasión.

Foto: Esparta Palma (Flickr CC-by)

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