Shell Script to check if file is of type Unix Executable File

Question

I am writing a Shell Script where user will pass the path to JAVA_HOME as a parameter. I wanted to check whether the JAVA_HOME path is valid or not. So how can I check whether the input path passed is a exe file ( Unix Executable File ) or not ? Suppose if users passed /usr/bin/java - which is valid, if user passes like /usr/bin/test.txt ( some text file )- which is not valid. So how can I check whether the file is of type Unix Executable File ?

I tried with -x , guess that is not the rite check , since it returns true for /usr/bin also !!!

Post a snippet of your script where you are seeing the problem. — rkyser
– rkyser, Commented Jul 31, 2012 at 18:16

Paul R · Accepted Answer · 2012-07-31 18:18:00Z

5

Easiest way is to use the file command.

$ file /usr/bin
/usr/bin: directory
$ file /usr/bin/java
/usr/bin/java: Mach-O universal binary with 2 architectures
/usr/bin/java (for architecture x86_64):    Mach-O 64-bit executable x86_64
/usr/bin/java (for architecture i386):  Mach-O executable i386
$

You can just grep the output of file for a suitable string, e.g. "executable".

answered Jul 31, 2012 at 18:18

Paul R

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dmckee --- ex-moderator kitten · Accepted Answer · 2012-07-31 18:21:13Z

The man page for test is quite clear that just -x isn't going to do it

-x file True if file exists and is executable. True indicates only that the execute flag is on. If file is a directory, true indicates that file can be searched.

But if you combine this with -f and -r

-f file True if file exists and is a regular file.

-r file True if file exists and is readable.

you will know if the file has the requisite properties to be an executable.

There remains the possibility that a user could have set these properties on a non-executable, but that would clearly be a user error.

Man page excerpt here taken from the Mac OS 10.5 versions. You may seem something slightly different on other systems (Linux in particular).

Icarus · Accepted Answer · 2012-07-31 18:18:52Z

0

Unix "executables" are anything that have the execute attribute set. You cannot rely on this since you can set execute permissions on a pdf document, for example.

Maybe what you ought to use to detect the type of file is the file command, instead. It will tell you whether the file is a binary or plain text, for example.

answered Jul 31, 2012 at 18:18

Icarus

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