Ubuntu – How to add a backslash before all spaces

command linesedtext processingtr

How can I put a backslash before every space, preferably by using tr or sed commands?

Here is my script:

#!/bin/bash
line="hello bye"
echo $line | tr ' ' "\\\ "

This is supposed to replace spaces with a backslash followed by a space, but it's only replacing the spaces with a backslash and not backlash+space.

This is the output I get:

hello\bye

Expected output:

hello\ bye

Best Answer

tr can't do multiple characters. Use one of these instead:

  1. sed

    echo "$line" | sed 's/ /\\ /g'

    or

    sed 's/ /\\ /g' <<< "$line"

  2. Perl

    echo "$line" | perl -pe 's/ /\\ /g'

    or

    perl -pe 's/ /\\ /g'<<< "$line"

    Perl also has a nifty function called quotemeta which can escape all odd things in a string:

    line='@!#$%^&*() _+"'
perl -ne 'print quotemeta($_)' <<< $line

    The above will print

    \@\!\#\$\%\^\&\*\(\)\ _\+\"\

  3. You can also use printf and %q:

    %q  quote the argument in a way that can be reused as shell input

    So, you could do

    echo "$line" | printf "%q\n"

    Note that this, like Perl's quotemeta will escape all special characters, not just spaces.

    printf "%q\n" <<<$line

  4. If you have the line in a variable, you could just do it directly in bash:

    echo ${line// /\\ }
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