Problems with for loops and : modifiers

Problems with for loops and : modifiers

[pleb]

I'm having problems doing something that should be simple. I want to iterate over a set of files in a directory and run some commands on those files. In the command I would like to strip the suffix of a filename away (ie basename) and add a new suffix.

I can do this interactively in zsh, using several of the different builtin "for" commands, but not in the following shell script.

Q:

1. Why do the "for" loops work interactively and get a syntax error in a script? To me a newline terminator is a newline terminator.

2. Maybe I have the sense of SHORT_LOOPS backward?

3. Why does the :r modifier work interactively and not in a script?

4. What are the suggested ways to do what I want to do?

zsh script follows.

Thanks in advance.

leb

#/bin/zsh

echo "one"
#files get echoed but :r is broken
for i in *.h; { echo $i:r ; }

echo "two"
#file get echoed, but :r is broken
for i in *.h
do
echo ${i}:r
done

echo "three"
# works perfectly when run interactively but gets an error in a script
#for i (*.h) echo $i:r

echo "four"
# works perfectly when run interactively but gets an error in a script
#foreach i ( *.h)
#echo $i:r
#end
#


-- 
Lawrence E. Bakst
pleb@iridescent.org

Re: Problems with for loops and : modifiers

[Peter Stephenson]

pleb@iridescent.org wrote:
> I'm having problems doing something that should be simple. I want to iterate 
> over a set of files in a directory and run some commands on those files. In t
> he command I would like to strip the suffix of a filename away (ie basename) 
> and add a new suffix.
> 
> I can do this interactively in zsh, using several of the different builtin "f
> or" commands, but not in the following shell script.
> 
> Q:
> 
> 1. Why do the "for" loops work interactively and get a syntax error in a scri
> pt? To me a newline terminator is a newline terminator.
> 
> 2. Maybe I have the sense of SHORT_LOOPS backward?
> 
> 3. Why does the :r modifier work interactively and not in a script?
> 
> 4. What are the suggested ways to do what I want to do?

It's possible you have different options set in .zshrc or /etc/zshrc.
Those won't be used in a script, only .zshenv or /etc/zshenv.  (I tend
to prefer to write scripts beginning `emulate zsh', which put the shell
into a known mode, and set any necessary options explicitly.)

> echo "two"
> #file get echoed, but :r is broken
> for i in *.h
> do
> echo ${i}:r
> done

Change the substitution to ${i:r}.  The ${...} insulates the parameter
substitution from other stuff around, so :r is not active.

You say $i:r is broken in the other example: the only thing I can find
that turns off modifiers is the ksh_arrays option.  Try adding `setopt
no_ksh_arrays' at the start of the script.  If that works, something in
/etc/zshenv or ~/.zshenv is setting it.

I'd recommend sticking with the form of `for' shown above in a script,
since it's standard and unambiguous.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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