Unix Shell脚本变量声明-找不到命令

Question

nOption=' | awk '{total+=$1} END {print total/1024"kb"}' '
find . -type f -printf "%s %p/n"| sort -nr | head -n10 $nOption

I would like to create a script to find the biggest file at current directory. This is my script, there had a error if I use the variable to substitute....

the output : ./big.sh: line 67: +=: command not found

but it works if i do not use variable :

find . -type f -printf "%s %p/n"| sort -nr | head -n10 | awk '{total+=$1} END {print total/1024"kb"}' 

the output is what should i want: 680.021kb

What's wrong of my script??

thank you

Answer 1

Single quoted strings cannot contain other single quotes, so that awk command is interpreted as a shell command instead. Putting commands in variables is tricky, and in general it's easier, safer and more readable to create a function:

nOption() {
    awk '{total+=$1} END {print total/1024"kb"}'
}
find . -type f -printf "%s %p/n"| sort -nr | head -n10 | nOption

For this specific case, as @chepner points out, the issue is that you can't put command separators such as | in a string and then execute that as part of a pipe (without eval , which is evil ).

Answer 2

The problem is with quotes inside quotes, in variable expansion...
Why don't go with a one-liner? It's a (tiny) bit faster, and sleeker... :-)

find . -type f -printf "%s %p/n"| sort -nr | head -n10 | awk '{total+=$1} END {print total/1024"kb"}'

---

Update :
To make the script more flexible, you could do:

dir="."
units="1024"
unitsstring="kb"
find "$dir" -type f -printf "%s %p/n"| sort -nr | head -n10 | awk '{total+=$1} END {print total/$units"$unitsstring"}'