[X4U] Decent book on scripting language

[David Ledger]

>From: Ed Gould <edgould1948 at comcast.net>
>I am spending way too much time doing a repetitive tasks of moving
>files around.
>I guess I need some sort of scripting language that will allow me to
>automate this task. I know I will never be able to totally automate
>it as (at times) it needs human judgement, but I can live with the
>"few" exceptions.
>
>Simply put I need to move a file from one folder to another folder
>(BUT) if there is a duplicate don't move it.
>   The from folder will remain constant but the receiving folder will
>change depending on the first character of the file.
>
>I am somewhat familiar with one or two other scripting languages but
>have zero knowledge on anything Apple might have.
>
>Can someone suggest a scripting language that will be able to test
>easily if a file exists and *move* files from foldera to folderb (or
>"c" or "d" or "e" etc)

There are plenty of choices.

'Applescript' is a language for non-programmers (so it used to say) 
and to someone who has been a programmer for 40 years (me) it's as 
clear as mud. The non-programmers it's designed for seem to have more 
success with it. 'Automator' seems to follow in its footsteps.

'Awk' is often overlooked as a language, but it good for working with 
data rather than manipulating the filesystem tree.

'Perl' is well known for its similarity to line noise, so if you're 
not a programmer, the learning curve is enormous. That's not to say 
it isn't a superb language for very many things. Like 'awk' its forte 
is data handling rather than file management.

csh/tcsh - two Unix 'Shell' languages. If you're used to languages 
with language elements neatly grouped with parentheses and brackets, 
these look like what you're used to. But they're badly implemented in 
some areas and once you get past the basics you can find some things 
that just aren't possible because there's no way to represent what 
you need.

sh/ksh/bash/posix-shell/zsh - a 'family' of vaguely related Unix 
Shell languages based on the almost original Unix Bourne Shell (by 
Stephen Bourne) that use the same type of syntax but with different 
capability extensions. The main differences are in many cases only to 
do with interactive use rather than scripting.

In 'sh' shells, you would need something like below. '#' starts a 
comment. I've added an unnecessary '#' to
the beginning of each comment-only line to help re-format the lines. 
Comment text is indented with the active statement lines. This is in 
short-form style. if...then...fi can be used.
Note that to move a file from foldera to folderb, both must be writable.

src=path_of_foldera
dst=path_of_folderb

[ -d $dst ] || exit        # test ([ ....]) that the variable 'dst' 
contains the path to a directory (-d)
#                              # '||' means 'or' or 'otherwise'
cd $src || exit            # 'cd' will fail if its argument is not 
the path of an existing directory
[ -w $src -a -w $dst ] || exit        # -w is the 'test for 
writeable' flag, -a here means 'and'
for file in *; do	# '*' expands to all filenames that don't 
start with a '.'
#                              # Each time round, variable 'file' is 
loaded with the next one
	[ -f $file ] || continue                  # test if the file 
whose name is in variable
#                                                              # 
'file' is a plain file (not a directory etc.)
#                                                              # skip 
and go to next if it isn't
                 [ -f $dst/$file ] || mv $file $dst/$file        # see 
the pattern of it?
done                         # end of the loop

Of these, only Perl can be made to do your sort of task itself, and 
that requires the use of the File module. The rest end up using 
another program to do the actual work. Applescript uses the Finder, 
the others would use the Unix utility 'mv'. This means that for 
general use, for Applescript you also need to learn the script 
capabilities of all the OS X utilities; for the others you need to 
learn the Unix commands.

There are many Unix command books but few on Applescript, and less on 
the scripting capabilities of OSX apps.

David






-- 
David Ledger - Freelance Unix Sysadmin in the UK.
HP-UX specialist of hpUG technical user group (www.hpug.org.uk)
david.ledger at ivdcs.co.uk
www.ivdcs.co.uk