time - time a simple command or give resource usage
time [options] command [arguments...]
The time command runs the specified program command with the given arguments. When command finishes, time writes a message to standard error giving timing statistics about this program run. These statistics consist of (i) the elapsed real time between invocation and termination, (ii) the user CPU time (the sum of the tms_utime and tms_cutime values in a struct tms as returned by times(2) ), and (iii) the system CPU time (the sum of the tms_stime and tms_cstime values in a struct tms as returned by times(2) ).
The variables LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, LC_NUMERIC, NLSPATH and PATH are used. The last one to search for command. The remaining ones for the text and formatting of the output.
If command was invoked, the exit status is that of command. Otherwise it is 127 if command could not be found, 126 if it could be found but could not be invoked, and some other non-zero value (1-125) if something else went wrong.
Below a description of the GNU 1.7 version of time. Disregarding the name of the utility, GNU makes it output lots of useful information, not only about time used, but also on other resources like memory, I/O and IPC calls (where available). The output is formatted using a format string that can be specified using the -f option or the TIME environment variable.
The default format string is
%Uuser %Ssystem %Eelapsed %PCPU (%Xtext+%Ddata %Mmax)k %Iinputs+%Ooutputs (%Fmajor+%Rminor)pagefaults %Wswaps
When the -p option is given the (portable) output format
The format string
The format is interpreted in the usual printf-like way. Ordinary characters are directly copied, tab, newline and backslash are escaped using \t, \n and \\, a percent sign is represented by %%, and otherwise % indicates a conversion. The program time will always add a trailing newline itself. The conversions follow. All of those used by tcsh(1) are supported.
-f FORMAT, --format=FORMAT
Specify output format, possibly overriding the format specified in the environment variable TIME.
--help Print a usage message on standard output and exit successfully.
Not all resources are measured by all versions of Unix, so some of the values might be reported as zero. The present selection was mostly inspired by the data provided by 4.2 or 4.3BSD.
GNU time version 1.7 is not yet localized. Thus, it does not implement the POSIX requirements.
The environment variable TIME was badly chosen. It is not unusual for systems like autoconf or make to use environment variables with the name of a utility to override the utility to be used. Uses like MORE or TIME for options to programs (instead of program path names) tend to lead to difficulties.
It seems unfortunate that -o overwrites instead of appends. (That is, the -a option should be the default.)
Mail suggestions and bug reports for GNU time to
Please include the version of time, which you can get by running time --version
and the operating system and C compiler you used.
tcsh(1) , times(2) , wait3(2)
POSIXization, autoconfiscation, GNU getoptization, documentation, other bug fixes and improvements.
Arne Henrik Juul
Helped with portability
Helped with portability
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