The other way of executing shell script???

[dayananda.ms]

Hi All,

Is there any other way of executing shell script??? other than below ones.

1) sh file.sh
2) source file.sh
3) .(dot) file.sh
4) ./file.sh

[GNU-Fan]

Yes.


(I am not going to mention them by name, because this could mislead you to the wrong assumption that this list was complete. )

[secondmouse]

5) piping
I'll give you a detail example for this:

I have a iptables script in /usr/bin as follows

/usr/bin/firewall-script
#!/bin/bash
...
iptables -t nat -A POSTROUTING -o eth1 -s 192.168.3.0/24 -j MASQUERADE
iptables -t nat -A POSTROUTING -o eth1 -s 192.168.10.0/24 -j MASQUERADE
...

for some reason I need to temporarily change eth1 to tun1 in the above script, the way to do that without modifying that script is to simply run

sed -e '/MASQUERADE/ s/eth1/tun1/g' /usr/bin/firewall-script | bash

[Cabhan]

For what it's worth, 2 and 3 in your list are the same thing. The dot is just a shortcut for "source".

Also note that sourcing a script is very different from running it normally. A sourced script exports all of its variable definitions to its parent:

tanya:bash alex$ cat sample_script 
#!/bin/bash

var=Hello

echo "My var is $var"
tanya:bash alex$ ./sample_script 
My var is Hello
tanya:bash alex$ echo $var

tanya:bash alex$ source sample_script 
My var is Hello
tanya:bash alex$ echo $var
Hello

You shouldn't use "source" unless you are doing it to get the variable definitions. Otherwise, use one of the other methods.


Also, 4 on your list is incomplete. What #4 actually is that you can give the full path of a script and it will execute that script. If the script is in the current directory, you can say "./SCRIPT", because "." means "the current directory". However, I could also say "/home/user/script" (absolute path: it starts with "/") or, "test/bash/script" (relative path from my current location).

[burschik]

Let's not forget exec.