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time(1)
NAME
time - Times the execution of a command
SYNOPSIS
time [-p] command [argument...]
The time command prints the elapsed time during the execution of a command,
the time spent in the system, and the time spent in execution of the
command on the diagnostic output system.
Note
The C shell has a built-in version of the time command. If you are
using the C shell, and want to guarantee that you are using the
command described here, you must specify the full path /usr/bin/time.
See the csh(1) reference page for a description of the built-in
command.
STANDARDS
Interfaces documented on this reference page conform to industry standards
as follows:
time: XPG4, XPG4-UNIX
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
OPTIONS
-p Writes the timing output to standard error. This is the default.
OPERANDS
command
The name of a command to be executed. If command identifies any name
specified as a special built in your applicable shell reference page,
the results are undefined and unpredictable.
argument
The argument to be passed to command. See the appropriate reference
pages for these values. This parameter may include flags and arguments
expected by command.
DESCRIPTION
The time command prints the elapsed time during the execution of a command,
the time spent in the system, and the time spent in execution of the
command on the diagnostic output system. Time is reported in seconds.
The time command (with a different format) is also built into csh.
NOTES
When time is used as part of a pipeline, the times reported are
unspecified, except when it is the sole command within a grouping command
in that pipeline. For example, the commands on the left are unspecified;
those on the right report on utilities a and c, respectively.
time a | b | c { time a } | b | c
a | b | time c a | b | (time c)
EXIT STATUS
The time command returns the following exit values if the command could not
be invoked:
1-125
An error occurred in the time command.
126 The command specified by command was found but could not be invoked.
127 The command specified by command could not be found.
If the command was successfully invoked, the exit status of time is the
exit status of command.
EXAMPLES
1. To measure the time required to run a program, enter:
time a.out
This runs the program a.out and writes to the standard error output
the amount of real, system, and user time that it uses:
real 10.5
user 0.3
sys 3.6
2. To measure the time required by a complex command, enter:
time sh -c 'complex-cmmand-line'
This runs all of the commands, which may include pipelines, and
returns the time information for the entire series of commands.
ENVIRONMENT VARIABLES
The following environment variables affect the execution of time:
LANG
Provides a default value for the internationalization variables that
are unset or null. If LANG is unset or null, the corresponding value
from the default locale is used. If any of the internationalization
variables contain an invalid setting, the utility behaves as if none of
the variables had been defined.
LC_ALL
If set to a non-empty string value, overrides the values of all the
other internationalization variables.
LC_CTYPE
Determines the locale for the interpretation of sequences of bytes of
text data as characters (for example, single-byte as opposed to
multibyte characters in arguments).
LC_MESSAGES
Determines the locale for the format and contents of diagnostic
messages written to standard error.
NLSPATH
Determines the location of message catalogues for the processing of
LC_MESSAGES.
PATH
Determines the path used to locate command.
SEE ALSO
Commands: csh(1), ksh(1), Bourne shell sh(1b), POSIX shell sh(1p)
Functions: times(3)
Standards: standards(5)