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What is this command doing?

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# 1  
Old 06-02-2010
What is this command doing?
Code:
auxiliar=`eval echo $PATH_LOG/${CAJA}_${FECHA}.log`
auxiliar=`grep '> CODIFICACION ESTADO' $auxiliar|cut -d ":" -f 3|tail -1`

what is the value in auxiliar after the 2 nd assignment?
Last edited by Scott; 06-02-2010 at 08:01 AM.. Reason: Code tags, please...
# 2  
Old 06-02-2010
Quote:
Originally Posted by samta
Code:
auxiliar=`eval echo $PATH_LOG/${CAJA}_${FECHA}.log`

eval seems unnecessary.
auxiliar will have the name of the file "$PATH_LOG/${CAJA}_${FECHA}.log" as value after the first command. You can verify it by doing
Code:
echo "$auxiliar"

Quote:
Code:
auxiliar=`grep '> CODIFICACION ESTADO' $auxiliar|cut -d ":" -f 3|tail -1`

before the command is executed, auxiliar should correspond to a file or list of files.
what the command does:
  • extract any line containing '> CODIFICACION ESTADO' in the list of files defined by $auxiliar
  • take the third field using ':' as delimiter
  • output only the last line
Hope this is clear enough for you (who can know the contents of the involved files)
Last edited by frans; 06-03-2010 at 02:04 AM.. Reason: correction of "content" to "name"
# 3  
Old 06-03-2010
what is the command doing?
I tried the first cmd, auxilar=`eval echo $PATH_LOG/${CAJA}_${FECHA}.log` --- this echos the filename not the content of the file

So, the second command checks in the filename(if the first command lists one or more files) which has string "> CODIFICACION ESTADO'' and then cuts the field 3 delimited by : and gives only last line. Is my understanding correct?

thanks in advance
# 4  
Old 06-03-2010
Quote:
Originally Posted by samta
I tried the first cmd, auxilar=`eval echo $PATH_LOG/${CAJA}_${FECHA}.log` --- this echos the filename not the content of the file
Oops, apologizes. But notice that it can simply be written
Code:
auxilar="$PATH_LOG/${CAJA}_${FECHA}.log"

and the both lines can be written in one like
Code:
auxiliar=`grep '> CODIFICACION ESTADO' $PATH_LOG/${CAJA}_${FECHA}.log | cut -d ":" -f 3 | tail -1`

which will do exactly the same than the two lines of script.

And YES, your understanding is correct.
Last edited by frans; 06-03-2010 at 02:08 AM.. Reason: adding response to question
# 5  
Old 06-03-2010
thanks, so searching the pattern is on Filename not on the content of the file?

---------- Post updated at 12:12 AM ---------- Previous update was at 12:09 AM ----------

Thanks Frans... Got it.. Smilie
# 6  
Old 06-03-2010
Quote:
Originally Posted by samta
thanks, so searching the pattern is on Filename not on the content of the file?
No !
The grep command searches for a pattern in the file contents !
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