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How to know where the core files come from?

 
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Top Forums UNIX for Dummies Questions & Answers How to know where the core files come from?
# 1  
Old 08-04-2010
How to know where the core files come from?
Hi,
I am trying to use "find / -name core -print | xargs rm -f " ,but it would delete all core files including some core files we do not want to delete.
I search privious posts,someone said "To check what a core file came from - use the file command"
I used man page to search file command,but cannot find useful infomation.
Can you give me some hits?
I am just beginer.
Thank you so much!
# 2  
Old 08-04-2010
if you want to be selective about which files to delete and which ones to keep, please check if the -ok action of find command is what you are looking for
Code:
       -ok command ;
	      Like  -exec  but	ask the user first (on the standard input); if
	      the response does not start with `y' or `Y', do not run the com-
	      mand,  and  return  false.   If the command is run, its standard
	      input is redirected from /dev/null.

# 3  
Old 08-04-2010
The output from the unix file command on a core file contains output similar to this:
Code:
core:      core file from 'cat' - received SIGQUIT

We can test for the phrase "core file from" and be certain that the file is actually a core file. Beware that the exact format of the output from "core" varies and be sure to test thoroughly.


On some unixes there are legitimate files and directories called "core". I've even seen a system with a user called "core".

Quote:
"find / -name core -print | xargs rm -f"
This construct commits you to try to delete everything called "core".


We can pipe the list of "core" files to a loop to let us do further checks.
By echoing the "rm" line we can test whether the script will do what we expect without actually deleting anything.


Code:
find // -type f -name core -print | while read filename
do
            filetype=`file "${filename}"|grep "core file from"|awk '{print $2}`
            if [ "${filetype}""X" = "core""X" ]
            then
                     # We have found a core file
                     echo rm "${filename}"
            fi
done

This User Gave Thanks to methyl For This Post:
lemon_06
# 4  
Old 08-05-2010
Thank you to both of you! They help me a lot.I am trying to do it again now.
Thanks!

---------- Post updated 08-05-10 at 06:44 PM ---------- Previous update was 08-04-10 at 07:47 PM ----------

Hi methyl,
One confused question.In yr code,you put "find // -type f -name core -print "
There is two "/" slash,why use that? I think it should be one slash,or I missing something??
Thanks!
# 5  
Old 08-05-2010
Two slashes (leading and trailing for the directory name) is an old habit from early unix. It is harmless. On some versions of unix it was necessary to make "find" follow links.
Nowadays you really need to specify "-follow" to get "find" to follow links.

It's a bit like typing the the trailing solidus in an URL in your browser. It used to be much quicker but is no longer necessary.
# 6  
Old 08-06-2010
My unix file command out put like this
core: ELF 32-bit MSB core file SPARC Version 1, from 'ls'
Now I am trying to modify yr codes,but still not working.
One thing I have a little bit confused.I cannot fully understand the part between "do done“

Can you explain more in details?
Thank you so much!
# 7  
Old 08-06-2010
Hmm Solaris is different again.
Quote:
core: ELF 32-bit MSB core file SPARC Version 1, from 'ls'
Original line:
Code:
filetype=`file "${filename}"|grep "core file from"|awk '{print $2}`

Becomes:
Code:
filetype=`file "${filename}"|grep "core file SPARC Version 1, from"|awk '{print $5}`

The code is intended to fish out the word "core" from the output of "file" where the output contains a sentence stating that it is a core file. The "grep" passes the whole line to awk which is why it is looking at $5 which is the 5th word along from your example output from "file". Obviously try "file" on a few core files to make sure that the output format is consistent.
 
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