How to manipulate awk variable NF in zsh?

Question

I have a simple command line:

uptime | awk '{print $(NF - 2)}'

In a bash shell, this works without a hitch, but when I run it in zsh, I get the following error:

title:5: command not found: NF

As usual this will be a pilot error (me not grokking how expansion works in zsh), but I cannot figure out what to do to get the same command to work in zsh.

[Edit]

The zsh version is 4.3.11 on OSX, and the output from set -xv; uptime | awk '{print $(NF - 2)}' is:

$ set -xv; uptime | awk '{print $(NF - 2)}'
title:5: command not found: NF
+zsh:3> uptime
+zsh:3> awk '{print $(NF - 2)}'
0.51
+precmd:1> title '%15<..<%~%<<' '%n@%m: %~'                                                                           
+title:1> [ '' '!=' true ']'
+title:2> [[ xterm-256color == screen* ]]
+title:4> [[ xterm-256color == xterm* ]]
+title:5> print -Pn '\e]2;%n@%m:\ %~\a'
+title:6> print -Pn '\e]1;%15\<..\<%~%\<\<\a'
+zsh:4> git_prompt_info
+git_prompt_info:1> ref=+git_prompt_info:1> ref='' 
+git_prompt_info:1> return
+zsh:4> vi_mode_prompt_info
+vi_mode_prompt_info:1> echo ''

So apparently the awk command works, but my terminal customization is borked.

Answer 1

title:5: command not found: NF

This error message shows an error in a function called title, which by the name presumably sets your terminal's title to the command being run. The subsequent transcript shows title being called by precmd, which is called when a command has finished executing, just before showing the next prompt. But the error is actually triggered by preexec, which is called just before running a command. This function is defined in your ~/.zshrc (or perhaps /etc/zshrc, or in a file that either of them calls).

I can't tell exactly what is wrong without seeing the code, but it looks like the command string is being expanded in some way. Perhaps you have the prompt_subst option set and are printing the command through print -P? You need to escape the command. In particular, do not print it through print -P, print it through print -r and take care of literal control characters. Something like:

print -r ${${${${(qqqq)1}#\$\'}%\'}//\\\'/'}