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Full Discussion: GREP loop
Homework and Emergencies Homework & Coursework Questions GREP loop Post 302771149 by bakunin on Tuesday 19th of February 2013 07:13:54 PM
Old 02-19-2013
Good so far. You are making some typical beginners errors, though:

Code:
RESULT=($(grep -irf searchwords /home | cut -d / -f3))

The outer "(...)" is superfluous, but the quoting is missing. Whenever a string might contain whitespace in a shell script you should quote it: first, to protect the whitespace from being interpreted away by the shell and second to make clear that the shell should not treat the whitespace as a separator.

Another thing is: you nowhere declare RESULT to be an array, but you treat it as one further down. Even if the shell allows for such liberty you should write your scripts as if it doesn't. In this case the outer braces are necessary but the subshell ("$(...)") isn't. The following should work:

Code:
typeset -a RESULT=(grep -irf searchwords /home | cut -d / -f3)

Code:
for USERLIST in ${RESULT[*]}

This is working but a dangerous way to loop through an array. The shell has a maximum line length (see "limits.h") and works on a lin in this way: first, all the variables are scanned and replaced by their value. Then the resulting line is evaluated. Depending on how big the array RESULT is the line could be pretty long and this could result in the shell rejecting the line with "line too long". Use a while-loop with an index counter instead:

Code:
(( iCnt = 0 ))
while [ $iCnt -lt ${#RESULT[*]} ] ; do
     do-something "${RESULT[$iCnt]}"
     (( iCnt += 1 ))
done

Code:
PHRASE=`grep -irf searchwords /home/$USERLIST | cut -d : -f2`
FLOC=`grep -irf searchwords /home/$USERLIST | cut -d : -f1`

This is possible, but a time-killer. You issue the same command twice, every time using a different part of the output instead of doing it once. Here is a trick: "read" can read in not only one but several variables:

Code:
grep -irf searchwords /home/$USERLIST | cut -d : -f1,2 | read FLOC PHRASE

This will do the same as your two lines above.

Code:
CHECKGOOD=`grep $USERLIST /opt/guser`

You do this - use of backtics - a lot. You shouldn't. backtics are outdated and deprecated and only supported for backwards compatibility reasons. You should use the subshell-command instead:

Code:
var=`command-list`    # wrong and to be avoided
var="$(command-list)"  # correct


I hope this helps.

bakunin

Last edited by bakunin; 02-19-2013 at 08:20 PM..
This User Gave Thanks to bakunin For This Post:
 

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