Question: I want to get rid of all invalid characters; example `hexadecimal value 0x1A` from an XML file using sed.  

What is the regex and the command line?   

EDIT  

Added Perl tag hoping to get more responses. I prefer a one-liner solution.  

EDIT  

These are the valid XML characters  

```
x9 | xA | xD | [x20-xD7FF] | [xE000-xFFFD] | [x10000-x10FFFF]

```

Answer: 
Assuming UTF-8 XML documents:

```
perl -CSDA -pe'
   s/[^\x9\xA\xD\x20-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}]+//g;
' file.xml > file_fixed.xml

```

If you want to encode the bad bytes instead,

```
perl -CSDA -pe'
   s/([^\x9\xA\xD\x20-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}])/
      "&#".ord($1).";"
   /xeg;
' file.xml > file_fixed.xml

```

You can call it a few different ways:

```
perl -CSDA     -pe'...' file.xml > file_fixed.xml
perl -CSDA -i~ -pe'...' file.xml     # Inplace with backup
perl -CSDA -i  -pe'...' file.xml     # Inplace without backup

```
The `tr` command would be simpler. So, try something like:

```
cat <filename> | tr -d '\032' > <newfilename>

```

Note that ascii character '0x1a' has the octal value '032', so we use that instead with `tr`. Not sure if `tr` likes hex.