How to find the maximum value for the field by ignoring the lines with characters using awk? - awk

Question

Since am newbie to the awk , please help me with your suggestions. I tried the below command to filter the maximum value and ignore the first & last lines from the sample text file separately. They work when I try them separately.
My query:
I need to ignore the last line and first few lines and from the file and then need to take the maximum value for the field 7 using awk .
I also need to ignore the lines with the characters . Can anyone suggest me the possibilities two use both the commands together and get the required output.
Sample file:
Linux 3.10.0-957.5.1.el7.x86_64 (j051s784) 11/24/2020 _x86_64_ (8 CPU)
12:00:02 AM kbmemfree kbmemused %memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty
12:10:01 AM 4430568 61359128 93.27 1271144 27094976 66771548 33.04 39005492 16343196 1348
12:20:01 AM 4423380 61366316 93.28 1271416 27102292 66769396 33.04 39012312 16344668 1152
12:30:04 AM 4406324 61383372 93.30 1271700 27108332 66821724 33.06 39028320 16343668 2084
12:40:01 AM 4404100 61385596 93.31 1271940 27107724 66799412 33.05 39031244 16344532 1044
06:30:04 PM kbmemfree kbmemused %memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty
07:20:01 PM 3754904 62034792 94.29 1306112 27555948 66658632 32.98 39532204 16476848 2156
Average: 4013043 61776653 93.90 1293268 27368986 66755606 33.03 39329729 16427160 2005
Commands used:
cat testfile | awk '{print $7}' | head -n -1 | tail -n+7
awk 'BEGIN{a= 0}{if ($7>0+a) a=$7} END{print a}' testfile
Expected output:
Maximum value for the column 7 by excluding the lines wherever alphabet character is available

Answer 1

1st solution(Generic solution): Adding one Generic solution here, where sending field name to an awk variable(which we want to look for for maximum value) it will automatically find out its field number from very first line and will work accordingly. Considering that your first line has that field name which you want to look for.
awk -v var="kbcached" '
FNR==1{
for(i=1;i<=NF;i++){
if($i==var){ field=i }
}
next
}
/kbmemused/{
next
}
{
if($2!~/^[AP]M$/){
val=$(field-1)
}
else{
val=$field
}
}
{
max=(max>val?max:val)
val=""
}
END{
print "Maximum value is:" max
}
' Input_file
2nd solution(As per shown samples only): Could you please try following, based on your shown samples only. I am assuming you want the field value of column kbcached.
awk '
/kbmemfree/{
next
}
{
if($2!~/^[AP]M$/){
val=$6
}
else{
val=$7
}
}
{
max=(max>val?max:val)
val=""
}
END{
print "Maximum value is:" max
}
' Input_file

Answer 2

awk '$7 ~ ^[[:digit:]]+$/ && $1 != "Average:" {
max[$7]=""
}
END {
PROCINFO["sorted_in"]="#ind_num_asc";
for (i in max) {
maxtot=i
}
print maxtot
}' file
One liner:
awk '$7 ~ /^[[:digit:]]+$/ && $1 != "Average:" { max[$7]="" } END { PROCINFO["sorted_in"]="#ind_num_asc";for (i in max) { maxtot=i } print maxtot }' file
Using GNU awk, search for lines where field 7 is only numbers and field one is not "Average:" In these instances, create an array entry with field 7 as the index. At the end, sort the array in index ascending number order. Loop through the array setting a maxtot variable. The last entry in the max array will be the highest kbcached and so print maxtot