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

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.

Answer 1

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

Answer 2

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