Unexpected latex error: Text line contains an invalid character

Question

My latex started showing this error:

Error | line 3|! Text line contains an invalid character.

out of nowhere. Actually, it shows 100 of this errors, all in the same line.

I started to investigate and tried to test where the error could come from. In the end I ended with the following code:

\documentclass[12pt,twoside]{report}
\begin{document}
  Hello $1,2,3$.
\end{document}

and the same error appears. I tried to remove the \documentclass but the same error appears. Here's a printscreen of the error(s);

If any of you guys would help me, this is driving me mad!

The log file:

LOG FILE : This is pdfTeX, Version 3.1415926-2.5-1.40.14 (MiKTeX 2.9 64-bit) (preloaded format=pdflatex 2015.6.27) 3 AUG 2015 17:47 entering extended mode

**main.tex ("C:\Users\Admin\Dropbox\Mestrado\Tese\Latex\Minhatese\main.tex" LaTeX2e <2011/06/27> Babel and hyphenation patterns for english, afrikaans, ancientgreek, ar abic, armenian, assamese, basque, bengali, bokmal, bulgarian, catalan, coptic, croatian, czech, danish, dutch, esperanto, estonian, farsi, finnish, french, ga lician, german, german-x-2013-05-26, greek, gujarati, hindi, hungarian, iceland ic, indonesian, interlingua, irish, italian, kannada, kurmanji, latin, latvian, lithuanian, malayalam, marathi, mongolian, mongolianlmc, monogreek, ngerman, n german-x-2013-05-26, nynorsk, oriya, panjabi, pinyin, polish, portuguese, roman ian, russian, sanskrit, serbian, slovak, slovenian, spanish, swedish, swissgerm an, tamil, telugu, turkish, turkmen, ukenglish, ukrainian, uppersorbian, usengl ishmax, welsh, loaded.

("C:\Program Files\MiKTeX2.9\tex\latex\base\report.cls" Document Class: >report 2007/10/19 v1.4h Standard LaTeX document class ("C:\Program >Files\MiKTeX 2.9\tex\latex\base\size12.clo" File: size12.clo 2007/10/19 v1.4h Standard >LaTeX file (size option) ) \c@part=\count79 \c@chapter=\count80 \c@section=\count81 \c@subsection=\count82 \c@subsubsection=\count83 \c@paragraph=\count84 \c@subparagraph=\count85 \c@figure=\count86 \c@table=\count87 \abovecaptionskip=\skip41 \belowcaptionskip=\skip42 \bibindent=\dimen102 )

("C:\Users\Admin\Dropbox\Mestrado\Tese\Latex\Minha tese\main.aux" !

Text line contains an invalid character. l.3 ... A funny symbol that I can't read has just been input. Continue and I'll forget it ever happened. ! Text line contains an invalid character. l.3 ... A funny symbol that I can't read has just been input. Continue and I'll forget it ever happened.

[... the same error over and over ...]

! ==> Fatal error occurred, no output PDF file produced!

Answer 1

Sometimes I get such errors due to corrupted auxiliary files, e.g. a truncated *.aux or such due to killing pdflatex. Other source can be "invisible" garbage in the file, which can be e.g. control characters that snuck in, or even some hilarity like a terminal escape that goes back and overwrites some junk with spaces. Another possibility is that you have characters in the file that look normal, but aren't (e.g. modern systems display UTF-8 text with little trouble; a Greek omicron looks like Latin o, but they are different characters; unless you set the encoding up for UTF-8 you'll get grief). Practical solution: Delete all intermediate files and try again. If the problem persists, open the file and retype the offending line, deleting the original. Sometimes you'd need to rewrite a paragraph to fix this.

Update: Just had an infuriating round with pdflatex because somehow I inserted some strange character (looked like a apostrophe, but wasn't --- next to invisible).

Answer 2

My assumption is that the wrong input file is used. Instead of the source file, LaTeX is given a binary file, like a PDF file, for example.

Another option is a wrong encoding. There is some support for UTF-8. But UTF-16 and UTF-32 are not supported. The added zero bytes also cause these kind of error.

When TeX is running, it generates a file with extension .log. This log shows you the input files as well as the complete error messages. Please, update the question to include the .log file (at least from the start up to the first error messages, no need for all error messages).

Answer 3

I would like to promote @melissa_boiko's comment to a full answer because it solved my related issue. Check if you have a running latexmk -pvc in another terminal window. If yes, kill it with Ctrl-C, remove all generated files (importantly .aux, maybe .bbl and others) and compile again.

@melissa_boiko's original comment (under @vonbrand's answer) from Feb 2018:

After adding some text, I was getting this error with trailing NULs (^@) at a random, unrelated line, and I could never grep them in the sources or find out how it was related to the change. I tried commenting out dangerous-looking lines but there seemed to be no pattern to how it reacted. Then I noticed that xelatex was giving me different results regardless of commenting; two runs in a row from identical sources might either compile ok, or break with invalid character. Turns out I had forgotten a latexmk -pvc process running in another tab, and I was competing with myself.

All thanks go to them.

Answer 4

When I compile with \documentclass{article}, it worked well. When I compile with your documentclass, it worked well. There may be problem with the compiler.

Answer 5

I just resolved this problem myself, which had a distinctive cause than those discussed above. For me, the problem was caused by Dropbox selective sync. I changed my the folder containing the tex files and all input files to be stored locally. That resolved the problem for me.

Answer 6

For me, this problem appeared after my computer crashed and rebooted. I had to delete both

*.aux
*.out

files for everything to start working again.

Answer 7

It's worth explaining in which situation will the error message appear.

They appear when a character from 0 → 31, or 127, appear in the input.

That is, null byte, or one of the control characters.

In the OP's case,

("C:\Users\Admin\Dropbox\Mestrado\Tese\Latex\Minha tese\main.aux"
! Text line contains an invalid character.

Because we know that TeX prints out ( followed by each file being input on the terminal, we deduce that the null (or otherwise invalid) byte is in the AUX file. So the solution is of course to delete it and retry. (if it doesn't work, the logical next step is to take a look at the file with some hexadecimal editor and see if an invalid byte is really there.)

That having said, sometimes it's because of the a.out file. Note that .out is also common extension for an executable (for compilers like GCC, the default output file name is a.out if you don't specify one), and an executable will overwhelmingly likely contain a null byte.

---

Technical detail: it is caused by a character with catcode 15. Viewing a character's catcode, and listing all characters with a given catcode can be used to list all characters with catcode 15.

Note that LuaTeX has another time where a slightly different "funny symbol" message is printed, namely:

static void utf_error(void)
{
    const char *hlp[] = {
        "A funny symbol that I can't read has just been (re)read.",
        "Just continue, I'll change it to 0xFFFD.",
        NULL
    };
    deletions_allowed = false;
    tex_error("String contains an invalid utf-8 sequence", hlp);
    deletions_allowed = true;
}

invalid UTF-8 sequence.