I try to customize a little BASH script for special proprose.
I'm confuse with BASH scripting when it come time to assigne a command to a variable.
My broken code:
if [ -n "$2" ]
then
top=`| head -n $2`
fi
awk '{print $17, ">", $19;}' $logs_folder$i | sort -g | uniq -c | sort -r -g $top
So by default it return all line but if the user specified a number, it will add the head command
Use array form instead:
if [ -n "$2" ]
then
top=(head -n "$2")
else
top=(cat)
fi
awk '{print $17, ">", $19;}' "$logs_folder$i" | sort -g | uniq -c | sort -r -g | "${top[@]}"
And try to add more quotes ("").
Actually you can't save pipe to a variable and let bash parse it the normal way when it's expanded but you can replace it with another command instead (cat).
You could actually use eval but it's pretty delicate:
if [ -n "$2" ]
then
top="| head -n \"\$2\""
fi
eval "awk '{print $17, \">\", \$19;}' \"\$logs_folder\$i\" | sort -g | uniq -c | sort -r -g $top"
A working script would look like this:
# set propper default value
top=""
if [ -n "$2" ]
then
# use double quotes instead of back-tics
# back-tics are for command substitution
# but you need the command itself as a string
top="| head -n $2"
fi
awk '{print $17, ">", $19;}' "$logs_folder$i" | sort -g | uniq -c | sort -r -g $top
