Time in ZSH

For instance, to measure the execution time of sleep cmd:

% time sleep 2
sleep 2  0.00s user 0.00s system 0% cpu 2.004 total

TIMEFMT

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The default output format for time cmd is: %J %U user %S system %P cpu %*E total And this can be changed by exporting TIMEFMT variable.

Common TIMEFMT Escape Sequences:

• %E: Elapsed time in seconds.
• %*E: Elapsed time in a human-readable format (e.g., 1:30.00).
• %U: CPU seconds spent in user mode.
• %S: CPU seconds spent in kernel/system mode.
• %P: CPU percentage utilization.
• %M: Maximum memory used (in Kbytes).

BASH-Like

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If you prefer the clean, standard three-line format used by bash:

% export TIMEFMT=$'real\t%E\nuser\t%U\nsys\t%S'

Fancy

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If you like me, who like fancy ANSI color and stay with zsh’s one-liner output:

% export TIMEFMT=$'"\e[1;4;93m%J\e[0m" completed in \e[92m%*E\e[0m [cpu: \e[1;91m%P\e[0m  mem: \e[1;96m%M\e[0mkb]'
% time sleep 2    
"sleep 2" completed in 2.006 [cpu: 0%  mem: 3kb]

REPORTIME

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Zsh has a powerful built-in feature that automatically displays execution times for any cmd that takes longer than a specified number of seconds.

% REPORTTIME=3
% timeout 3s zsh -c 'while :; do :; done'  
"timeout 3s zsh -c 'while :; do :; done'" completed in 3.002 [cpu: 99%  mem: 3kb]

GNU Time

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In zsh, time is a shell reserved word rather than a standard built-in command or standalone binary.

If you need to bypass the zsh reserved word and call the OS GNU/Unix time binary directly:

% /usr/bin/time -p sleep 2
# OR
% \time -p sleep 2