Libreoffice file conversion problem on centOS

I am using centOS 6.5 and libreoffice packages all installed. When I am trying to convert document using command line getting error.I can’t recognize the problem.

I am using following command

libreoffice --headless -convert-to html resume.docx 2>&1


soffice -env:UserInstallation=file:MY_PATH --headless --convert-to pdf:writer_pdf_Export --outdir files 11.ppt 2>&1


/usr/lib/libreoffice/program/soffice.bin --headless --convert-to pdf:writer_pdf_Export --outdir files 11.ppt 2>&1

When exceute the above command I am getting following error

/usr/lib/libreoffice/program/soffice.bin X11 error: Can't open display:

Set DISPLAY environment variable, use -display option or check permissions of your X-Server

(See "man X" resp. "man xhost" for details)

The --headless argument simply supresses the GUI but I recall reading a developer statement that there is still an X dependency. Perhaps add the --nologo or --display argument as listed on the help page.