UNIX for Dummies Questions & Answers

Hello all,

Can someone explain to me the advantage between using subshell over a function call in scripts? To me these are the same. Am I wrong to think this?

When you place a block of commands in between parenthesis instead of curly brackets, a subshell is created to run the commands instead of just running them in the current shell.

The subshell command sequence is done in a subprocess. This means that changing a process-specific characteristic (for example, the current directory) won't affect the current process after the subshell is finished.

However, if you change a process-specific characteristic, such as the current directory, inside a function, then when the function is finished, the current directory remains changed. That could be a good thing or a bad thing, depending on what you want.

The above comments are very important to understand, but a subshell will actually spawn a new shell process. For example, time the two following scripts to see which is faster:
#1

Code:

#! /bin/ksh
n=0
until (( n == 1000 )); do
     print Huh? >/dev/null
     ((n=n+1))
done

#2

Code:

#! /bin/ksh
n=0
until (( n == 1000 )); do
     ( print Huh? >/dev/null ; )
     ((n=n+1))
done

I should mention that I cannot test this at the moment, so I might be giving a bad example...

They were both too fast to time in seconds, but the first script definately executed faster than the second script.

Thank you oombera and LivinFree for your reply . I think I got it now.