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Full Discussion: Looping structure to make up for lack of bash GOTO
Top Forums Shell Programming and Scripting Looping structure to make up for lack of bash GOTO Post 302904208 by LMHmedchem on Monday 2nd of June 2014 10:25:03 PM
Old 06-02-2014
Looping structure to make up for lack of bash GOTO
Hello,

I am re-processing some files when a specific condition is met. The condition is read from the filename. Since files may need to be re-processed a number of times before they no longer meet the condition, I need to know when to stop re-processing. I am having trouble visualizing the proper control structure. What I had in mind was something like,
Code:
1: look through the list of files and find those that meet the re-process condition
2: increment a counter to track the number of files that meet the contrition
3: re-process files that meet the condition
4: GOTO 1 unless the counter==0

The above code would nicely keep looping until there were no compliment files found. The somewhat annoying lack of a GOTO statement makes takes this option off of the table, so I need a replacement.

I guess that some kind of a while loop would be the best alternative, but I don't know what bash has to offer for loops other than a do loop.

Can someone make a suggestion for this. I can post more code if that would help.

---------- Post updated at 10:25 PM ---------- Previous update was at 08:44 PM ----------

At the moment, I am trying something like this,
Code:
# zero stop condition
STOP=0

 # keep looping until stop condition is met
 while [ "$STOP" -ne "1" ] 
 do

   ###create list of current files
   $FILES

   ### check list for re-process condition and add filename to array
   for FILENAME in $FILES
   do
      if [ "$VALUE1" == "$VALUE2" ]; then
         FILENAMES_TO_PROCESS=("${FILENAMES_TO_PROCESS[@]}" "$FILENAME")
      fi
   done

   ### check if any files were found to re-process
   # if no files are found that meet the re-process condition
   if [ "${#FILENAMES_TO_PROCESS[@]}" == "0" ]; then
      echo "no files require reprocessing"
      # set condition to exit while loop
      STOP=1
   # if files are found, re-process files on the list
   else
      # rm file that is being reprocessed
      # code to reprocess files that need it
      ...
   if

   # do statistics on re-processed files, this will create an updated filename for any re-processed file
   # filenames of re-processed files will be re-checked on next loop

done

As far as I can tell, this will re-process all files that need it. Re-processing will create a new set of file names. The code will loop back to check the new set of file names to see if anything still needs to be re-processed. The code will keep looping until no file names are found that need to be re-processed.

I still seem to be incapable of writing code without multiple nested loops.

Is there anything wrong with this that so far?

LMHmedchem
 

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LEARN ABOUT DEBIAN

alien::package::rpm

Alien::Package::Rpm(3pm)				User Contributed Perl Documentation				  Alien::Package::Rpm(3pm)

NAME

       Alien::Package::Rpm - an object that represents a rpm package

DESCRIPTION

       This is an object class that represents a rpm package. It is derived from Alien::Package.

FIELDS

       prefixes
	   Relocatable rpm packages have a prefixes field.

METHODS

       checkfile
	   Detect rpm files by their extention.

       install
	   Install a rpm. If RPMINSTALLOPT is set in the environement, the options in it are passed to rpm on its command line.

       scan
	   Implement the scan method to read a rpm file.

       unpack
	   Implement the unpack method to unpack a rpm file. This is a little nasty because it has to handle relocatable rpms and has to do a bit
	   of permissions fixing as well.

       prep
	   Prepare for package building by generating the spec file.

       cleantree
	   Delete the spec file.

       build
	   Build a rpm. If RPMBUILDOPT is set in the environement, the options in it are passed to rpm on its command line.

	   An optional parameter, if passed, can be used to specify the program to use to build the rpm. It defaults to rpmbuild.

       version
	   Set/get version.

	   When retreiving the version, remove any dashes in it.

       postinst
       postrm
       preinst
       prerm
	   Set/get script fields.

	   When retrieving a value, we have to do some truely sick mangling. Since debian/slackware scripts can be anything -- perl programs or
	   binary files -- and rpm is limited to only shell scripts, we need to encode the files and add a scrap of shell script to make it
	   unextract and run on the fly.

	   When setting a value, we do some mangling too. Rpm maintainer scripts are typically shell scripts, but often lack the leading shebang
	   line.  This can confuse dpkg, so add the shebang if it looks like there is no shebang magic already in place.

	   Additionally, it's not uncommon for rpm maintainer scripts to contain bashisms, which can be triggered when they are ran on systems
	   where /bin/sh is not bash. To work around this, the shebang line of the scripts is changed to use bash.

	   Also, if the rpm is relocatable, the script could refer to RPM_INSTALL_PREFIX, which is set by rpm at run time. Deal with this by
	   adding code to the script to set RPM_INSTALL_PREFIX.

       arch
	   Set/get arch field. When the arch field is set, some sanitizing is done first to convert it to the debian format used internally. When
	   it's retreived it's converted back to rpm form from the internal form.

AUTHOR

       Joey Hess <joey@kitenet.net>

perl v5.14.2							    2011-08-05						  Alien::Package::Rpm(3pm)
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