需要帮助从bash脚本中的awk引用转义

Question

I have an alias in my bashrc file that outputs current folder contents and system available storage, updated continuously by the watch function.

alias wtch='watch -n 0 -t "du -sch * -B 1000000 2>/dev/null | sort -h && df -h -B 1000000| head -2 | awk '{print \$4}'"'

The string worked fine until I put in the awk part. I know I need to escape the single quotation marks, while still staying in the double quotation marks and the $4 but I haven't been able to get it to work. What am I doing wrong?

This is the error I get

-bash: alias: $4}": not found

Answer 1

Since the quoting for the alias is making it tough, you could just make it a function instead:

wtch() {
    watch -n 0 -t "du -sch * -B 1000000 2>/dev/null | sort -h && df -h -B 1000000| head -2 | awk '{print $4}'"
}

This is a lot like issue 2 in the BashFAQ/050

Also, a minor thing but you can skip the head process at the end and just have awk do it, even exiting after the second row like

wtch() {
    watch -n 0 -t "du -sch * -B 1000000 2>/dev/null | sort -h && df -h -B 1000000| awk '{print $4} NR >= 3 {exit}'"
}

Answer 2

In this case you can use cut instead of awk . And you'll have the same effect.

alias wtch="watch -n 0 -t 'du -sch * -B 1000000 2>/dev/null | sort -h && df -h -B 1000000| head -2 | cut -d\  -f4'"

Explaining cut :

-d option defines a delimiter
-d\  means that my delimiter is space
-f selects a column
-f4 gives you the fourth column