Manual browser: time(1)

TIME(1) General Commands Manual TIME(1)


timetime command execution


time [-clp] command [argument ...]


The time utility executes and times command. After the command finishes, time writes the total elapsed time (wall clock time), (“real”), the CPU time spent executing command at user level (“user”), and the CPU time spent executing in the operating system kernel (“sys”), to the standard error stream. Times are reported in seconds.

Available options:

Displays information in the format used by the time builtin of csh(1).
Lists resource utilization information. The contents of the command process's rusage structure are printed; see below.
The output is formatted as specified by IEEE Std 1003.2-1992 (“POSIX.2”).

Some shells, such as csh(1) and ksh(1), have their own and syntactically different built-in version of time. The utility described here is available as /usr/bin/time to users of these shells.

Resource Utilization

If the -l option is given, the following resource usage information is displayed in addition to the timing information:
  • maximum resident set size
  • average shared memory size
  • average unshared data size
  • average unshared stack size
  • page reclaims
  • page faults
  • swaps
  • block input operations
  • block output operations
  • messages sent
  • messages received
  • signals received
  • voluntary context switches
  • involuntary context switches
Resource usage is the total for the execution of command and any child processes it spawns, as per wait4(2).




The time utility exits with one of the following values:
An error occurred in the time utility.
The command was found but could not be invoked.
The command could not be found.

Otherwise, the exit status of time will be that of command.


The time utility conforms to IEEE Std 1003.2-1992 (“POSIX.2”).


The granularity of seconds on microprocessors is crude and can result in times being reported for CPU usage which are too large by a second.
November 9, 2011 NetBSD 7.0