How to replace value of place holder

Question

I am new to shell programming. I have two files:

eg.txt
file.sh

The eg.txt file has some HTML content and file.sh cotains a shell script. In the script a value is assigned to the temp variable, and that value should be injected into the HTML file.

eg.txt

<html>
  Hi MGM ,<br/>
  One alert has been received !!<br/>

 Here is the event Data.<br/><br/>

 <font size=‘1’>{temp}</font>
 <br/><br/>
 Regards,
 WDTS Supports.
 </html>

file.sh

echo $1
temp=56

(
echo "To:"$1
echo "Subject: Alert Updates !! "
echo "Content-Type: text/html"

echo cat eg.txt
) | /usr/sbin/sendmail -t

echo "Mail sent !!"

Remember `!` has special meanings in bash. Check [\[ this \]](http://serverfault.com/questions/208265/what-is-bash-event-not-found). — sjsam, Jun 03 '16 at 06:26

SLePort · Answer 1 · 2016-06-03T07:25:29.330

3

With sed :

sed "s/{temp}/$temp/" eg.txt | /usr/sbin/sendmail -t

You can also use printf to inject variables in your template :

file.sh

temp=56
tpl=$(cat "eg.txt")

printf "$tpl" "$1" "$temp" | /usr/sbin/sendmail -t

eg.txt

To:%s
Subject: Alert Updates !!
Content-Type: text/html

<html>
  Hi MGM ,<br/>
  One alert has been received !!<br/>

 Here is the event Data.<br/><br/>

 <font size=‘1’>%s</font>
 <br/><br/>
 Regards,
 WDTS Supports.
 </html>

Update:

If multiple variables, just write multiple substitute commands (and update placeholders in eg.txt):

sed "s/{temp1}/$temp1/;s/{temp2}/$temp2/" eg.txt | /usr/sbin/sendmail -t

edited Jun 03 '16 at 07:25

answered Jun 03 '16 at 05:51

SLePort

15,211
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No harm in addinf the `g` with sed I guess but why bother? ;) – sjsam Jun 03 '16 at 05:54
I am working this command, but emails are going to spam. Can anyone tell me how to deal with this. It should come in my inbox – Harkirat Singh Lamba Jun 03 '16 at 06:35
Try to remove the `!!` from Subject in eg.txt – SLePort Jun 03 '16 at 06:46
@Kenavoz i was working with multilple temp like temp 1 temp 2 etc but its not giving me answer. – Harkirat Singh Lamba Jun 03 '16 at 06:54
What do to tou watt to achieve with thèse temps variables? You should édit your question – SLePort Jun 03 '16 at 07:02
@Kenavoz i had taken temp=56 in last example. Now i am taking two more variable like temp1=34, temp2=45. So i want to know how to write sed for this ? – Harkirat Singh Lamba Jun 03 '16 at 07:05

score 2 · Answer 2 · edited Apr 13 '17 at 12:36

I have introduced some error checking to your code :

#!/bin/bash
temp=56
if [ -z "$1" ]
then
echo "Usage : ./file.sh user_name_to_mail to"
exit -1
else
    if id "$1" >/dev/null 2>&1 #Check if user exists, suppress stdout, stderr
    then
      mail_header=$(echo -e "To: $1\nSubject: Alert Updates"'!!'"\nContent-Type: text/html\n")
      mail_body=$(awk -v var="$temp" '{print gensub(/{temp}/,var,"g"$0)}' eg.txt)
      echo -e "$mail_header\n$mail_body" | sendmail -t                   
    else
      echo -e "Sorry! Invalid User\n"
      exit -1 # The error code is set to  detect failure
    fi
fi

To prevent the mails going to spam you need to have a valid SPF record for domain from which you're sending email. Check [ this ] for a starting point.

Note:

! is a special character to bash, it is used to refer to previous command. To work around this problem I have used ..Updates"'!!'"\nContent-Type...

Inside the single quotes the ! loses its special meaning.

Interesting reads :

What is an [ SPF ] record?
Open SPF [ documentation ] .

I don't agree, to be honest I don't see how it can be more explicit than: `if this_thing; then`. Wrapping in command substitutions implies OP is familiar with `$?`. And even if they are, it's still practice to teach. — Andreas Louv, Jun 03 '16 at 08:04

Chet · Answer 3 · 2016-06-03T06:13:17.360

1

echo $1
temp=56

    (
    echo "To:"$1
    echo "Subject: Alert Updates !! "
    echo "Content-Type: text/html"

    awk -F "" -v var=$temp '{gsub(/{temp}/,var,$0); print}' < eg.txt 
) | /usr/sbin/sendmail -t

echo "Mail sent !!"

added awk to '|' where the temp is stored in awk variable : var which is later replaced

awk -F "" -v var=$temp '{gsub(/{temp}/,var,$0); print}'

edited Jun 03 '16 at 06:13

answered Jun 03 '16 at 05:47

Chet

1,205
1
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2

Beware: [UUoC](https://stackoverflow.com/questions/11710552/useless-use-of-cat/) — Useless Use of `cat`. – Jonathan Leffler Jun 03 '16 at 06:10
Working with this command but emails are going in spam. How to resolve this. Emails should come in Inbox. – Harkirat Singh Lamba Jun 03 '16 at 06:38

How to replace value of place holder

3 Answers3