How do I determine file encoding in OS X?

I'm trying to enter some UTF-8 characters into a LaTeX file in TextMate (which says its default encoding is UTF-8), but LaTeX doesn't seem to understand them.

Running cat my_file.tex shows the characters properly in Terminal. Running ls -al shows something I've never seen before: an "@" by the file listing:

-rw-r--r--@  1 me      users      2021 Feb 11 18:05 my_file.tex

(And, yes, I'm using \usepackage[utf8]{inputenc} in the LaTeX.)

I've found iconv, but that doesn't seem to be able to tell me what the encoding is -- it'll only convert once I figure it out.

Using the -I (that's a capital i) option on the file command seems to show the file encoding.

file -I {filename}

In Mac OS X the command file -I (capital i) will give you the proper character set so long as the file you are testing contains characters outside of the basic ASCII range.

For instance if you go into Terminal and use vi to create a file eg. vi test.txt then insert some characters and include an accented character (try ALT-e followed by e) then save the file.

They type file -I text.txt and you should get a result like this:

test.txt: text/plain; charset=utf-8

The @ means that the file has extended file attributes associated with it. You can query them using the getxattr() function.

There's no definite way to detect the encoding of a file. Read this answer, it explains why.

There's a command line tool, enca, that attempts to guess the encoding. You might want to check it out.

vim -c 'execute "silent !echo " . &fileencoding | q' {filename}

aliased somewhere in my bash configuration as

alias vic="vim -c 'execute \"silent \!echo \" . &fileencoding | q'"

so I just type

vic {filename}

On my vanilla OSX Yosemite, it yields more precise results than "file -I":

$ file -I pdfs/udocument0.pdf
pdfs/udocument0.pdf: application/pdf; charset=binary
$ vic pdfs/udocument0.pdf
latin1
$
$ file -I pdfs/t0.pdf
pdfs/t0.pdf: application/pdf; charset=us-ascii
$ vic pdfs/t0.pdf
utf-8

You can also convert from one file type to another using the following command :

iconv -f original_charset -t new_charset originalfile > newfile

e.g.

iconv -f utf-16le -t utf-8 file1.txt > file2.txt

Just use:

file -I <filename>

That's it.

Using file command with the --mime-encoding option (e.g. file --mime-encoding some_file.txt) instead of the -I option works on OS X and has the added benefit of omitting the mime type, "text/plain", which you probably don't care about.

Classic 8-bit LaTeX is very restricted in which UTF8 characters it can use; it's highly dependent on the encoding of the font you're using and which glyphs that font has available.

Since you don't give a specific example, it's hard to know exactly where the problem is — whether you're attempting to use a glyph that your font doesn't have or whether you're not using the correct font encoding in the first place.

Here's a minimal example showing how a few UTF8 characters can be used in a LaTeX document:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[utf8]{inputenc}
\begin{document}
‘Héllø—thêrè.’
\end{document}

You may have more luck with the [utf8x] encoding, but be slightly warned that it's no longer supported and has some idiosyncrasies compared with [utf8] (as far as I recall; it's been a while since I've looked at it). But if it does the trick, that's all that matters for you.

The @ sign means the file has extended attributes. xattr file shows what attributes it has, xattr -l file shows the attribute values too (which can be large sometimes — try e.g. xattr /System/Library/Fonts/HelveLTMM to see an old-style font that exists in the resource fork).

Typing file myfile.tex in a terminal can sometimes tell you the encoding and type of file using a series of algorithms and magic numbers. It's fairly useful but don't rely on it providing concrete or reliable information.

A Localizable.strings file (found in localised Mac OS X applications) is typically reported to be a UTF-16 C source file.

Synalyze It! allows to compare text or bytes in all encodings the ICU library offers. Using that feature you usually see immediately which code page makes sense for your data.

You can try loading the file into a firefox window then go to View - Character Encoding. There should be a check mark next to the file's encoding type.

I implemented the bash script below, it works for me.

It first tries to iconv from the encoding returned by file --mime-encoding to utf-8.

If that fails, it goes through all encodings and shows the diff between the original and re-encoded file. It skips over encodings that produce a large diff output ("large" as defined by the MAX_DIFF_LINES variable or the second input argument), since those are most likely the wrong encoding.

If "bad things" happen as a result of using this script, don't blame me. There's a rm -f in there, so there be monsters. I tried to prevent adverse effects by using it on files with a random suffix, but I'm not making any promises.

Tested on Darwin 15.6.0.

#!/bin/bash

if [[ $# -lt 1 ]]
then
  echo "ERROR: need one input argument: file of which the enconding is to be detected."
  exit 3
fi

if [ ! -e "$1" ]
then
  echo "ERROR: cannot find file '$1'"
  exit 3
fi

if [[ $# -ge 2 ]]
then
  MAX_DIFF_LINES=$2
else
  MAX_DIFF_LINES=10
fi


#try the easy way
ENCOD=$(file --mime-encoding $1 | awk '{print $2}')
#check if this enconding is valid
iconv -f $ENCOD -t utf-8 $1 &> /dev/null
if [ $? -eq 0 ]
then
  echo $ENCOD
  exit 0
fi

#hard way, need the user to visually check the difference between the original and re-encoded files
for i in $(iconv -l | awk '{print $1}')
do
  SINK=$1.$i.$RANDOM
  iconv -f $i -t utf-8 $1 2> /dev/null > $SINK
  if [ $? -eq 0 ]
  then
    DIFF=$(diff $1 $SINK)
    if [ ! -z "$DIFF" ] && [ $(echo "$DIFF" | wc -l) -le $MAX_DIFF_LINES ]
    then
      echo "===== $i ====="
      echo "$DIFF"
      echo "Does that make sense [N/y]"
      read $ANSWER
      if [ "$ANSWER" == "y" ] || [ "$ANSWER" == "Y" ]
      then
        echo $i
        exit 0
      fi
    fi
  fi
  #clean up re-encoded file
  rm -f $SINK
done

echo "None of the encondings worked. You're stuck."
exit 3

Which LaTeX are you using? When I was using teTeX, I had to manually download the unicode package and add this to my .tex files:

% UTF-8 stuff
\usepackage[notipa]{ucs}
\usepackage[utf8x]{inputenc}
\usepackage[T1]{fontenc}

Now, I've switched over to XeTeX from the TeXlive 2008 package (here), it is even more simple:

% UTF-8 stuff
\usepackage{fontspec}
\usepackage{xunicode}

As for detection of a file's encoding, you could play with file(1) (but it is rather limited) but like someone else said, it is difficult.

A brute-force way to check the encoding might just be to check the file in a hex editor or similar. (or write a program to check) Look at the binary data in the file. The UTF-8 format is fairly easy to recognize. All ASCII characters are single bytes with values below 128 (0x80) Multibyte sequences follow the pattern shown in the wiki article

If you can find a simpler way to get a program to verify the encoding for you, that's obviously a shortcut, but if all else fails, this would do the trick.