Adding BOM to UTF-8 files

I'm searching (without success) for a script, which would work as a batch file and allow me to prepend a UTF-8 text file with a BOM if it doesn't have one.

Neither the language it is written in (perl, python, c, bash) nor the OS it works on, matters to me. I have access to a wide range of computers.

I've found a lot of scripts to do the reverse (strip the BOM), which sounds to me as kind of silly, as many Windows program will have trouble reading UTF-8 text files if they don't have a BOM.

Did I miss the obvious?

Thanks!

I wrote this addbom.sh using the 'file' command and ICU's 'uconv' command.

#!/bin/sh

if [ $# -eq 0 ]
then
        echo usage $0 files ...
        exit 1
fi

for file in "$@"
do
        echo "# Processing: $file" 1>&2
        if [ ! -f "$file" ]
        then
                echo Not a file: "$file" 1>&2
                exit 1
        fi
        TYPE=`file - < "$file" | cut -d: -f2`
        if echo "$TYPE" | grep -q '(with BOM)'
        then
                echo "# $file already has BOM, skipping." 1>&2
        else
                ( mv "${file}" "${file}"~ && uconv -f utf-8 -t utf-8 --add-signature < "${file}~" > "${file}" ) || ( echo Error processing "$file" 1>&2 ; exit 1)
        fi
done

edit: Added quotes around the mv arguments. Thanks @DirkR and glad this script has been so helpful!

The easiest way I found for this is

#!/usr/bin/env bash

#Add BOM to the new file
printf '\xEF\xBB\xBF' > with_bom.txt

# Append the content of the source file to the new file
cat source_file.txt >> with_bom.txt

I know it uses an external program (cat)... but it will do the job easily in bash

Tested on osx but should work on linux as well

NOTE that it assumes that the file doesn't already have BOM (!)

(Answer based on https://stackoverflow.com/a/9815107/1260896 by yingted)

To add BOMs to the all the files that start with "foo-", you can use sed. sed has an option to make a backup.

sed -i '1s/^\(\xef\xbb\xbf\)\?/\xef\xbb\xbf/' foo-*

If you know for sure there is no BOM already, you can simplify the command:

sed -i '1s/^/\xef\xbb\xbf/' foo-*

Make sure you need to set UTF-8, because i.e. UTF-16 is different (otherwise check How can I re-add a unicode byte order marker in linux?)

Adding BOM to UTF-8 files

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