Shell Programming and Scripting

Hi all,

I just spent 30hours writing a script (my first) that makes extensive use of the find command on my mac os x terminal and which was meant to be run as a cron job on my server. The script is an automated backup system for a bunch of source control repositories. On the mac it works perfectly, but on the server, it fails miserably.


An example of a line of code that fails on the server:

Code:

modified=`stat -f "%Sm" -t "%c" $repoPath/$file`

Have I just received my first painful lesson that Linux is not the same as Unix or could I be doing something wrong at a more basic level?

Hi, cpower.

Welcome to the forums.

Thanks for using code markups, that helps with readability.

Please explain more about how your command fails. It is also useful if you tell us what version of OS X you are using as well as the distribution of Linux, what shell you are referring to, and perhaps the exact text of the error message you are receiving (if any) -- the Sherlock Holmeses here usually need evidence to solve mysteries ... cheers, drl

Thanks for the quick reply. Since my first post, I re-wrote the whole script following the man pages on my server rather than on the mac and it works perfectly.

What I'm still lost on however is the difference between the bash flavors. I understand that Mac OSX 10 is BSD unix based and my server is running a GNU/Linux bash, but other than finding different entries for certain man pages, I cant find any other references to shell scripts not being compatable between the two systems. Even more confusing for me is that the environment was set to the Bourne Shell. Shouldn't this be 100% compatible?

The bash versions as reported by each bash:
Macbook pro:

Code:

/bin/bash --version
GNU bash, version 3.2.17(1)-release (i386-apple-darwin9.0)
Copyright (C) 2005 Free Software Foundation, Inc.

Media temple gridserver:

Code:

/bin/bash --version
GNU bash, version 2.05b.0(1)-release (i386-pc-linux-gnu)
Copyright (C) 2002 Free Software Foundation, Inc.

Bump..?

Hi.

There will be some feature differences between versions of bash. However, if you are beginning learning Linux or BSD, those will be unlikely to bite you (famous last words).

I think you are far more likely to run into trouble with the gross and subtle differences in the commands of the two systems.

Perhaps something long the lines of BSD For Linux Users :: Intro may be useful ... cheers, drl

Good article - I'll have a read. Thanks.

That's a very old version of bash.

When writing scripts, especially those that must run in more than one environment, use only POSIX-compliant syntax and standard commands. Some commands, like stat, come in different versions with different options on different systems (and many do not even have such a command).