NAME
time —
time command execution
SYNOPSIS
time |
[-clp]
command [argument
...] |
DESCRIPTION
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:
-
-
- -c
- Displays information in the format used by the
time builtin of
csh(1).
-
-
- -l
- Lists resource utilization information. The contents of the
command process's rusage structure
are printed; see below.
-
-
- -p
- 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).
FILES
- ⟨sys/resource.h⟩
-
EXIT STATUS
The
time utility exits with one of the following values:
-
-
- 1-125
- An error occurred in the time
utility.
-
-
- 126
- The command was found but could not
be invoked.
-
-
- 127
- The command could not be found.
Otherwise, the exit status of
time will be that of
command.
SEE ALSO
csh(1),
ksh(1),
clock_gettime(2),
getrusage(2),
wait4(2)
STANDARDS
The
time utility conforms to
IEEE Std
1003.2-1992 (“POSIX.2”).
BUGS
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.