How to find the difference between a script file and a binary file?

$ ls -l /usr/bin
total 200732

-rwxr-xr-x 1 root   root     156344 Oct  4  2013 adb
-rwxr-xr-x 1 root   root       6123 Oct  8  2013 add-apt-repository
 list goes long ---------

In the above adb is a binary file and add-apt-repository is a script file.I get this information by viewing the files through nautilus.But through command line, i didn't find any differences.I can't able to predict these are binary files and these are script files.
So how do I differentiate between script and binary files through the command-line?

Just use file:

$ file /usr/bin/add-apt-repository
/usr/bin/add-apt-repository: Python script, ASCII text executable
$ file /usr/bin/ab
/usr/bin/ab: ELF 64-bit LSB  shared object, x86-64, version 1 (SYSV), dynamically

 linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=569314a9c4458e72e

4ac66cb043e9a1fdf0b55b7, stripped

As explained in man file:

NAME
   file — determine file type

DESCRIPTION
 This manual page documents version 5.14 of the file command.

 file tests each argument in an attempt to classify it.  There are three
 sets of tests, performed in this order: filesystem tests, magic tests,
 and language tests.  The first test that succeeds causes the file type to
 be printed.

 The type printed will usually contain one of the words text (the file
 contains only printing characters and a few common control characters and
 is probably safe to read on an ASCII terminal), executable (the file con‐
 tains the result of compiling a program in a form understandable to some
 UNIX kernel or another), or data meaning anything else (data is usually
 “binary” or non-printable).  Exceptions are well-known file formats (core
 files, tar archives) that are known to contain binary data.  When adding
 local definitions to /etc/magic, make sure to preserve these keywords.
 Users depend on knowing that all the readable files in a directory have
 the word “text” printed.  Don't do as Berkeley did and change “shell
 commands text” to “shell script”.

You can also use a trick to run this directly on the name of the executable in your $PATH:

$ file $(type -p add-apt-repository | awk '{print $NF}')
/usr/local/bin/add-apt-repository: Python script, ASCII text executable
$ file $(type -p ab | awk '{print $NF}')
/usr/bin/ab: ELF 64-bit LSB  shared object, x86-64, version 1 (SYSV), dynamically

 linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=569314a9c4458e

72e4ac66cb043e9a1fdf0b55b7, stripped

---

To find the file type of all executables that can be found in the directories of your $PATH, you can do this:

find $(printf "$PATH" | sed 's/:/ /g') -type f | xargs file

And to run file on all files in a particular directory (/usr/bin, for example), just do

file /usr/bin/*