How to store the grep output into a variable inside a loop?

Question

I would like to count the number of outputs produced by this loop

cd /System/Library/Extensions
find *.kext -prune -type d | while read d; do
     codesign -v "$d" 2>&1 | grep "invalid signature"
done

How can I store or count the outputs? If tried with arrays, counters etc. but it seems I can't get anything outside of that loop.

you need the count for each codesign -v "$d" 2>&1 or overall count of the while loop? — nu11p01n73R
– nu11p01n73R, Commented Nov 8, 2014 at 10:59

nu11p01n73R · Accepted Answer · 2014-11-08 11:05:48Z

3

To obtain the number of lines produced by the while loop, the wc word count can be used

cd /System/Library/Extensions
find *.kext -prune -type d | while read d; do
     codesign -v "$d" 2>&1 | grep "invalid signature"
done | wc -l

wc -l the -l option counts the number of lines in the input, which is piped to the output of while

Now if you need to count the number of grep outputs in each iteration of the while loop, the -c option of grep would be usefull.

cd /System/Library/Extensions
find *.kext -prune -type d | while read d; do
    codesign -v "$d" 2>&1 | grep -c "invalid signature"
done

-c Suppress normal output; instead print a count of matching lines for each input file

answered Nov 8, 2014 at 11:05

nu11p01n73R

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2 Comments

DavidD Over a year ago

Thanks a lot! the wc -l command did the trick. Two things I ended up changing: 1) I added "| tr -d ' '" after "wc -l", to remove a couple unwanted spaces that were appearing in the output. 2) I stored the result in a variable by wrapping the code as such: output=$(code)

nu11p01n73R Over a year ago

@DavidD You are always welcome :) glad to know i was of some help

philippe lhardy · Accepted Answer · 2014-11-08 19:01:14Z

classical difficulty in subshell is to pass variables back.

here one way to get this information back :

cd /System/Library/Extensions

RESULT=$(find *.kext -prune -type d | {
# we are in a sub-subshell ... 
GCOUNT=0
DIRCOUNT=0
FAILDIR=0
while read d; do
     COUNT=$(codesign -v "$d" 2>&1 | grep -c "invalid signature")
     if [[ -n $COUNT ]]
     then
     if [[ $COUNT > 0 ]]
     then
         echo "[ERROR] $COUNT invalid signature found in $d" >&2
         GCOUNT=$(( $GCOUNT + $COUNT ))
         FAILDIR=$(( $FAILDIR + 1 ))
     fi
     else
     echo "[ERROR] wrong invalid signature count for $d" >&2
     fi
     DIRCOUNT=$(( $DIRCOUNT + 1 ))
done
# this is the actual result, that's why all other output of this subshell are redirected
echo "$DIRCOUNT $FAILDIR $GCOUNT"
})

# parse result integers separated by a space.
if [[ $RESULT =~ ([0-9]+)\ ([0-9]+)\ ([0-9]+) ]]
then
    DIRCOUNT=${BASH_REMATCH[1]}
    FAILDIR=${BASH_REMATCH[2]}
    COUNT=${BASH_REMATCH[3]}
else
    echo "[ERROR] Invalid result format. Please check your script $0" >&2
fi

if [[ -n $COUNT ]]
then
    echo "$COUNT errors found in $FAILDIR/$DIRCOUNT directories"
fi

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