sed command throwing error in bash script

Question

I have a simple Bash shell Script to loop through each file in a directory and check is the copyright message is at the top of the file. If it's not there is should add it.

The script is giving an error when I try to use a variable in the sed command. I have looked at other similar questions and tried double quotes "", I have tried using a different operator but still can't find the solution. Can someone possibly point out what I am doing wrong?

Msg='/*------------------------------------------------------------------------------
*******************************************************************************
* Copyright message here
*******************************************************************************
*----------------------------------------------------------------------------*/'

for file in * 
  do
    if grep -Fxq "$Msg" $file
      then
        echo Marvel Message already exist: $file
    else
      if test -f "$file" 
        then
         echo "Adding Message to file: $file"
         sed -i "1s/^/${Msg}\n/" $file
      fi
    fi
done

You need to use delimiters that aren't included in the variable, i.e not / — 123
– 123, Commented Mar 13, 2018 at 13:59
I have tried setting the delimiter to | as in sed -i "1s|^|${Msg}\n|" $file but still issues — Ms_Marvel
– Ms_Marvel, Commented Mar 13, 2018 at 14:08
Possible duplicate of sed replace with variable with multiple lines — kvantour
– kvantour, Commented Mar 13, 2018 at 16:29
Have a look at sed replace with variable with multiple lines. There you see that you should replace your sed line with sed -i "1s/^/${Msg//$'\n'/\\n}\n/" $file — kvantour
– kvantour, Commented Mar 13, 2018 at 16:30
No, no, no, no. Don't use sed at all for this. Just do: { echo "$Msg"; cat "$file"; } > $file.tmp; mv $file.tmp $file Add some traps for cleanup if you want, and stop fooling yourself that sed -i will magically protect you from accidentally leaving tmp files on your filesystem. — William Pursell
– William Pursell, Commented Mar 13, 2018 at 16:49

glenn jackman · Accepted Answer · 2018-03-13 14:23:53Z

2

I would not use sed for this. I would use ed:

ed "$file" <<END
1i
$Msg
.
wq
END

Or, using sponge from the moreutils package

{ echo "$Msg"; cat "$file"; } | sponge "$file"

answered Mar 13, 2018 at 14:23

glenn jackman

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1 Comment

Ms_Marvel Over a year ago

I ended up using the pipe sponge, but also used @William Pursell approach mentioned above. Thanks guys

tripleee · Accepted Answer · 2018-03-13 17:04:56Z

0

Simply you can do it with marge like this, here with echo "$Msg" > tmp.txt you are creating a file with your $Msg as header of the tmp file. And with cat $file >> tmp.txt you are merging the file.

for file in * 
do
if grep -Fxq "$Msg" "$file"
  then
    echo Marvel Message already exist: "$file"
else
  if test -f "$file" 
    then
     echo "Adding Message to file: $file"
     #sed -i "1s/^/${Msg}\n/" $file
     echo "$Msg" > tmp.txt
     cat "$file" >> tmp.txt
     mv tmp.txt "$file"
   fi
 fi
done

Hope this will help you.

edited Mar 13, 2018 at 17:04

tripleee

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answered Mar 13, 2018 at 15:41

Abhijit Pritam Dutta

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