Difference between sh file.sh and file.sh

Question

I have two questions :

What is the difference between executing sh filename.sh and filename.sh?
How can I make both of them giving me the same output ?

I'm asking this question as right now I'm facing a problem. I'm trying to run a Java + SWT application from terminal.

When I do filename.sh, it gives me the desired output. But when I do sh filename.sh or bash filename.sh, it throws me an error :

Exception in thread "main" java.lang.NoClassDefFoundError: MainForm/java
Caused by: java.lang.ClassNotFoundException: MainForm.java
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Could not find the main class: MainForm.java.  Program will exit.

I know this question is already asked here but I'm still not clear about it.

I have gone through the following links :

What is the difference between ./ and sh to run a script?

Can scripts run even when they are not set as executable?

Can anyone help me with this?

If the script is not too long could you maybe post it? Pastebin is also ok — Gerhard Burger, Dec 07 '12 at 18:29

score 3 · Answer 1 · answered Oct 16 '12 at 10:32

3

The script probably knows which shell it should be running in. The first line might be something like

#!/bin/bash

If you run it with sh, the first line (a.k.a. shebang) is ignored. A different shell tries to run the script, but does not understand it - it is like running Java code in Pascal. If you run it with the right shell, it should behave identically:

/bin/bash script.sh

answered Oct 16 '12 at 10:32

choroba

9,643

Do you mean the 1st line of my filename.sh? – RAS Oct 16 '12 at 10:33
@RAS: Yes, exactly. – choroba Oct 16 '12 at 10:34
First line of my filename.sh is java -classpath .:jars – RAS Oct 16 '12 at 10:57
@RAS: Hm... what output do you get if you run sh filename.sh in a terminal? – choroba Oct 16 '12 at 10:58
Exception mentioned in the question. – RAS Oct 16 '12 at 11:10
Oh, I see. What do you get from echo $SHELL? – choroba Oct 16 '12 at 11:11
I'm getting : /bin/bash – RAS Oct 16 '12 at 11:14
Does ./filename.sh work? – choroba Oct 16 '12 at 11:15
No it doesn't. Gives me the same exception. – RAS Oct 16 '12 at 11:17
Try type filename.sh. You are probably calling a different script. – choroba Oct 16 '12 at 11:18
output : filename.sh is hashed (path to filename.sh) – RAS Oct 16 '12 at 11:23
And if you run path to filename.sh? – choroba Oct 16 '12 at 11:25
let us continue this discussion in chat – RAS Oct 16 '12 at 11:26

score 1 · Answer 2 · answered Oct 16 '12 at 11:24

1

By putting bash or sh before your file, you force to use this shell to execute your file. So it's better to use the first line of the file :

#!/path/to/shell

So every time you execute your file it will be with the same shell.

And for your second question, no, you need to make a script executable to run it :

chmod +x file.sh

answered Oct 16 '12 at 11:24

NorTicUs

2,382

You mean giving permission for "Execute : Allow executing file as program" ? – RAS Oct 16 '12 at 11:49
I'm not familiar with GUI, I was talking about a command you have to type in Terminal. But it sounds like the same thing, so give that a try. – NorTicUs Oct 16 '12 at 11:57
I asked you this as I already have gone through this link : http://askubuntu.com/questions/122428/how-to-run-sh-file – RAS Oct 16 '12 at 12:02
That's it. So what's your point ? – NorTicUs Oct 16 '12 at 12:14
When I do sh filename.sh or bash filename.sh, it throws me an error. – RAS Oct 16 '12 at 12:24
If you're referring to the error from the question, it's a Java error. Most likely, you're missing the classpath so it didn't find the main Java class – NorTicUs Oct 16 '12 at 12:29
But then why it runs successfully when I do filename.sh only? – RAS Oct 16 '12 at 13:07
let us continue this discussion in chat – NorTicUs Oct 16 '12 at 13:14

Difference between sh file.sh and file.sh

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