Shell Programming and Scripting

I have a script that when run creates 4 other text files. Sometimes a couple of these text files are empty. So what I am trying to do is find out if there is text in the file and if not delete the file.

What I have so far is the following script. I am just not sure how to return a true value in the grep. In Applescript it is easy but this shell scripting I am just starting out with.

#!/bin/sh

#testgrep-used to find a pattern in text file and if does not #exist then deletes file.


if grep "search_pattern" file_to_search
then rm file_to_search
exit 0
fi

Any help will be much appreciated and I am glad that I found these forums.

Thank You...

What is moving you from the applescript world into shell programming?

A very simple way to accomplish what you are describing is:

find /path/to/files -empty -exec rm -f {}\;

Cheers,

Keith

With Just a little modification

grep "search_pattern" file_to_search
if [ $? -eq 0 ]
then rm file_to_search
exit 0
fi

Thanks for the repies so quickly, but a couple of things happen.

When I execute this

find /path/to/files -empty -exec rm -f {}\;

and I put in the /path/to/file I get an error of -exec: no terminating ";" although there is one there.

Also when I put this in a script all by itself and fill in the appropriate areas nothing happens, it just returns to the next line

grep "search_pattern" file_to_search
if [ $? -eq 0 ]
then rm file_to_search
exit 0
fi

Could you please explain the second line.


Experimentation and sometimes it takes the Finder forever to do some things. In applescript you have to open applications most of the time to get the work done but with shell scripting and a text delimited file it is amazing how fast it is to use awk and/or sed (I still have not figured all of those out yet) to get the same job done. But I still use applescript most of the time because I have not figured out how to do my work in a shell script, such as taking 10000-11000 pictures and making a copy, cropping the copy to a certain size, making a thumbnail, renaming the thumbnail, apply a watermark to the cropped image, and putting each file into a separate directory, etc. all in a matter of about 8 minutes.

Proper spacing is important in the command I showed you.

As for your next question, most commands have a return value associated with them. 'grep' is going to return the number of times a pattern is matched, thus is 0 it found no matches. Are you wanting to remove empty files or files that don't have a pattern you want in them?

Cheers,

Keith

If the file does not contain the search pattern I would like to delete the file.

The second line checks if the command on the first line
executed properly(--grep found the pattern in the file)
and if an exit value of 0 is returned(i.e. command executed properly) it then removes the file <file_to_search>

Cheers!!