Time

$ /usr/bin/time --help
Usage: /usr/bin/time [OPTIONS] COMMAND [ARG]...
Run COMMAND, then print system resource usage.

-a, --append       with -o FILE, append instead of overwriting
-f, --format=FORMAT    use the specified FORMAT instead of the default
-o, --output=FILE     write to FILE instead of STDERR
-p, --portability     print POSIX standard 1003.2 conformant string:
real %%e
user %%U
sys %%S
-q, --quiet        do not print information about abnormal program
termination (non-zero exit codes or signals)
-v, --verbose       print all resource usage information instead of
the default format
-h, --help        display this help and exit
-V, --version      output version information and exit

Commonly usaged format sequences for -f/--format:
(see documentation for full list)
%%  a literal '%'
%C  command line and arguments
%c  involuntary context switches
%E  elapsed real time (wall clock) in [hour:]min:sec
%e  elapsed real time (wall clock) in seconds
%F  major page faults
%M  maximum resident set size in KB
%P  percent of CPU this job got
%R  minor page faults
%S  system (kernel) time in seconds
%U  user time in seconds
%w  voluntary context switches
%x  exit status of command

Default output format:
%Uuser %Ssystem %Eelapsed %PCPU (%Xavgtext+%Davgdata %Mmaxresident)k
%Iinputs+%Ooutputs (%Fmajor+%Rminor)pagefaults %Wswaps

NOTE: your shell may have its own version of time, which usually supersedes
the version described here. Please refer to your shell's documentation
for details about the options it supports.

GNU Time website: <https://www.gnu.org/software/time/>
Full documentation at: <https://www.gnu.org/software/time/manual>
E-mail bug reports to: bug-time@gnu.org

$ help time
time: time [-p] Pipeline
Report time consumed by pipeline's execution.

Execute PIPELINE and print a summary of the real time, user CPU time,
and system CPU time spent executing PIPELINE when it terminates.

Options:
-p    print the timing summary in the portable Posix format

The value of the TIMEFORMAT variable is used as the output format.

Exit Status:
The return status is the return status of PIPELINE.

$ whereis time
time: 
/usr/bin/time /usr/share/man/man7/time.7.gz 
/usr/share/man/man2/time.2.gz 
/usr/share/man/man1/time.1.gz 
/usr/share/man/man3/time.3am.gz 
/usr/share/info/time.info.gz

$ type time
time Ist ein reserviertes Schlüsselwort der Shell.

$ whatis time
time (1)       - run programs and summarize system resource usage
time (2)       - get time in seconds
time (3am)      - time functions for gawk
time (7)       - overview of time and timers