Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I need a simple way to check if my files are valid documents (pdf, doc, docx, ppt, pptx, xls, xlsx, odt, ods, odp and etc).

I can't use file because magic does not work well at all. For example, for PDF files, this is my output.

sweb@sweb-laptop: /media/files/ebooks/PDF and CHM$ file --mime *. Pdf
PHP 5 for Dummies. Pdf: application/pdf; charset=binary
PHP 6 and MySQL 5 for Dynamic Web Sites. Pdf: application/octet-stream; charset=binary
PHP6 and MySQL Bible. Pdf: application/pdf; charset=binary
PHP6.pdf: application/octet-stream; charset=binary
PHP and MySQL for Dummies SE. Pdf: application/pdf; charset=binary

For example, I use abiword – which is a good tool – but it converts any format. It doesn't check for valid documents:

abiword --to=txt --to-name=output.txt audio.mp3

Is there any command available to check for valid documents then?

share|improve this question
Excellent question. I'd like to know the answer to this as well. – Julian Knight Jun 25 '12 at 12:22
Sorry, somehow that formatting was messed up. Hope it's fixed now! – slhck Jun 25 '12 at 12:30
@slhck ty for improve – sweb Jun 25 '12 at 12:31

Update your /usr/share/file/magic file?

# pdf:  file(1) magic for Portable Document Format

0 string    %PDF-   PDF document
>5  byte    x   \b, version %c
>7  byte    x   \b.%c

I'd use hexdump to look at the first few bytes of the PDFs that are not identified correctly.


How you update the magic file depends on your operating system and distribution. Typically you'd use the package manager. For example on RedHat Linux and downstream distributions that follow, you can use yum provides /usr/share/file/magic to find what package contains that file then use sudo yum update <packagename> ...

$ yum provides /usr/share/file/magic
file-4.17-15.el5_3.1.x86_64 : A utility for determining file types.
Repo        : installed
Matched from:
Other       : Provides-match: /usr/share/file/magic

$ sudo yum update file
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base:
 * extras:
 * rpmforge:
 * updates:
Setting up Update Process
Resolving Dependencies
--> Running transaction check
---> Package file.x86_64 0:4.17-21 set to be updated
rpmforge/filelists_db                                    | 5.9 MB     00:08
updates/filelists_db                                     | 1.9 MB     00:03
--> Finished Dependency Resolution

Dependencies Resolved

 Package          Arch               Version             Repository        Size
 file             x86_64             4.17-21             base             320 k

Transaction Summary
Install       0 Package(s)
Upgrade       1 Package(s)

Total download size: 320 k
Is this ok [y/N]: y
Downloading Packages:
file-4.17-21.x86_64.rpm                                  | 320 kB     00:02
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
  Updating       : file                                                     1/2
  Cleanup        : file                                                     2/2

  file.x86_64 0:4.17-21


If you are willing, you can instead update the magic file using a text editor after reading man magic and using hexdump _C -n 20 on sample document files to work out signatures for yourself.

if you are going to do this, it might be prudent to create a separate magic file first and use files -m magicfile option to test it.


$ file --mime `locate *.pdf`
/usr/share/doc/bind-9.3.6/arm/Bv9ARM.pdf:                application/pdf
/usr/share/doc/libtheora-1.0alpha7/Theora_I_spec.pdf:    application/pdf
/usr/share/doc/prelink-0.4.0/prelink.pdf:                application/pdf
/usr/share/doc/samba-3.0.33/Samba3-ByExample.pdf:        application/pdf
/usr/share/doc/samba-3.0.33/Samba3-Developers-Guide.pdf: application/pdf
/usr/share/doc/samba-3.0.33/Samba3-HOWTO.pdf:            application/pdf
/usr/share/doc/speex-1.0.5/manual.pdf:                   application/pdf
/usr/share/ghostscript/8.70/examples/annots.pdf:         application/pdf
/usr/share/gimp-print/doc/users-guide.pdf:               application/pdf

Maybe you can upload, to a file-sharing website, some files that file fails to identify correctly.

share|improve this answer
how can i update it ? where is master branch of magic file ? – sweb Jun 25 '12 at 13:11
@sweb: see updated answer – RedGrittyBrick Jun 25 '12 at 13:34

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .