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Old 09-03-2003, 01:10 PM   #1
deadlock
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bash for loop problem


After some earlier help in this forum I have created a bash script that watches for files in a folder "in" and outputs pdf files to an "out" folder. During testing however, I have found that there is a problem when the loop is blank.

The basic code is as follows:

cd in
for file in *
do
// create pdf for $file
done

However when the folder "in" is empty, linux insists on passing a file "*" back to the script. This that messes up the logging of events and the pdf distiller.

I have tried putting a line such as:

if $file <> "*"

but bash gives an error at the line

Any suggestions?

(the for file in * was the best solution for the earlier problems)

Cheers

Dan
 
Old 09-03-2003, 01:46 PM   #2
david_ross
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Try using ls:
Code:
for file in `ls /path/to/in/*`
do
// create pdf for $file
done
 
Old 09-03-2003, 03:19 PM   #3
Strike
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Using make might be a better idea for this, just as an aside.
 
Old 09-04-2003, 03:47 AM   #4
deadlock
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Thanks

I have tried using

for file in ls...

and had problems with spaces and command chars in file names being interpreted by bash - unfortunately I need to be able to treat the names exactly as they are.

How do you mean use make???

Dan
 
Old 09-04-2003, 05:08 AM   #5
unSpawn
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If you execute your script in debug mode (sh -x <script>) you'd see the "for" loop breaking the results from "ls" up. If you use a "while" loop it won't. Only listing files with for instance the .ps extension limits the output of "ls", basename strips the extension which comes in handy when moving if your create_pdf_cmd doesn't output to stdout and doesn't have output options.

Code:
ls in/*.ps|while read file; do
filen=$(basename "$file" .ps)
create_pdf_cmd "$file" > in/"$filen".pdf
mv in/"$filen".pdf out; done
...or with "xargs" if you don't want to use a "while" loop. You're not restricted to using "ls" as well. If you know your input filetype always is Postscript and has a postscript extension, you could use
Code:
find in -type f -name \*.ps|xargs -ix ps2pdf "x"
else skip the "-name \*.ps" part. Note I don't use curly braces, I use "-ix" to get quoted variable x.
 
Old 09-04-2003, 05:32 AM   #6
deadlock
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That looks great, one quick question. The source files will either be .ps or .prn, which ghostscript copes with equally well, so the ls command I am using is:

Code:
ls $dir/in/{*.ps,*.prn}|while....
However if the "in" directory is empty, or there are no .ps files (and are .prn files) I get an on-screen error such as:

Code:
ls: .../in/*.ps: No such file or directory
As I want this script to be run on a cron, I obviously don't want to have messages filling up the log. As this error is obviously useless (as I don't need to know the folders empty) would a redirect to /dev/null be OK? e.g.

Code:
ls $dir/in/{*.ps,*.prn} 2>/dev/null|while....
or do I need to redirect the results to the while loop?

Also, can I get the basename command to cope with the 2 different extensions?

Dan

Last edited by deadlock; 09-04-2003 at 05:39 AM.
 
  


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