Question

I am doing some find/replace thing with sed and using tee to write output file.Here is the command

    # $1 source
    # $2 Type
    # $3 name 
    # $4 body 

    sudo sed  "s/<!--ID-->/1/g"  ./templates/tpl.txt \
        | sed  "s/<!--AUTHOR-->/myname/g"  \
        | sed  "s/<!--TYPE-->/$2/g"  \
        | sed  "s/<!--BODY-->/$4/g"  \
        | sed  "s/<!--NAME-->/$3/g"  \
        | tee  "$3.txt" > /dev/null

In the output file I see “n” in place of new lines . I need the same effect of as of the following
(but after template substitution )

 echo -e "$4" > "$3.txt"

I am bash learner and please help me furnish my code

Edit

$4 contains multiline string (e.g a mysql function /procedure or trigger ) with comments etc

thanks

Answer 1

If you plan to use tee for writting privileged files, you have to use sudo with tee.

You could:

sed < template/tpl.txt -e "
    s/<!--ID-->/1/g;
    s/<!--AUTHOR-->/myname/g;
    s/<!--TYPE-->/$2/g;
    s/<!--NAME-->/$3/g;
    /<!--BODY-->/{s/<!--BODY-->/$4/;s/\\n/\n/g;}
  " | sudo tee "$3" >/dev/null

other way: in bash ,you could use:

echo "${4//\\n/$'\n'}" 

so:

sed "s/<!--BODY-->/${4//\\n/$'\n'}/;"

could work too.

With Mac’s sed this may work better:

sed < template/tpl.txt "s/<\!--ID-->/1/g;
     s/<\!--AUTHOR-->/myname/g;
     s/<\!--TYPE-->/$2/g;
     s/<\!--BODY-->/${4//\\n/\\$'\n'}/
  " | sudo tee "$3" >/dev/null

Explanation: ${4//\\n/\\$'\n'} are bashism, we could use as you use bash. Mac sed don’t support \n as newline, but support a newline if escaped by a backslash \, so in RHS, \n could be written (in bash): \\$'\n' :

echo abc\\$'\n'def
abc\
def