documentclass[border=5mm]{standalone}
usepackage{tabularx}
begin{document}

begin{tabularx}{1.0linewidth}{X}
  header 1 \
  [unit 1) \
end{tabularx}
end{document}

Running `LaTeX' on `table_line_start' with ``pdflatex  -file-line-error   -interaction=nonstopmode "input" table_line_start.tex''
This is pdfTeX, Version 3.14159265-2.6-1.40.18 (TeX Live 2017) (preloaded format=pdflatex)
restricted write18 enabled.
entering extended mode
LaTeX2e <2017-04-15>
Babel <3.16> and hyphenation patterns for 84 language(s) loaded.
(./table_line_start.tex
(/usr/local/texlive/2017/texmf-dist/tex/latex/standalone/standalone.cls
Document Class: standalone 2015/07/15 v1.2 Class to compile TeX sub-files standalone
(/usr/local/texlive/2017/texmf-dist/tex/generic/oberdiek/ifluatex.sty)
(/usr/local/texlive/2017/texmf-dist/tex/generic/oberdiek/ifpdf.sty)
(/usr/local/texlive/2017/texmf-dist/tex/generic/ifxetex/ifxetex.sty)
(/usr/local/texlive/2017/texmf-dist/tex/latex/xkeyval/xkeyval.sty
(/usr/local/texlive/2017/texmf-dist/tex/generic/xkeyval/xkeyval.tex
(/usr/local/texlive/2017/texmf-dist/tex/generic/xkeyval/xkvutils.tex
(/usr/local/texlive/2017/texmf-dist/tex/generic/xkeyval/keyval.tex))))
(/usr/local/texlive/2017/texmf-dist/tex/latex/standalone/standalone.cfg)
(/usr/local/texlive/2017/texmf-dist/tex/latex/base/article.cls
Document Class: article 2014/09/29 v1.4h Standard LaTeX document class
(/usr/local/texlive/2017/texmf-dist/tex/latex/base/size10.clo)))
(/usr/local/texlive/2017/texmf-dist/tex/latex/tools/tabularx.sty
(/usr/local/texlive/2017/texmf-dist/tex/latex/tools/array.sty))
(./table_line_start.aux)
./table_line_start.tex:10: Argument of @argarraycr has an extra }.
<inserted text>
               par
l.10 end{tabularx}

Runaway argument?
unit 1) \ endtabular
./table_line_start.tex:10: Paragraph ended before @argarraycr was complete.
<to be read again>
               par
l.10 end{tabularx}

...

(That makes 100 errors; please try again.)
./table_line_start.tex:10:  ==> Fatal error occurred, no output PDF file produced!
Transcript written on table_line_start.log.

TeX Output exited abnormally with code 1 at Tue Feb 20 13:50:51

documentclass[border=5mm]{standalone}
usepackage{tabularx}
begin{document}

begin{tabularx}{1.0linewidth}{X}
  header 1 \
  {[unit 1)}
end{tabularx}
end{document}