1TIME(1) Linux User's Manual TIME(1)
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6 time - time a simple command or give resource usage
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9 time [options] command [arguments...]
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12 The time command runs the specified program command with the given
13 arguments. When command finishes, time writes a message to standard
14 error giving timing statistics about this program run. These statis‐
15 tics consist of (i) the elapsed real time between invocation and termi‐
16 nation, (ii) the user CPU time (the sum of the tms_utime and tms_cutime
17 values in a struct tms as returned by times(2)), and (iii) the system
18 CPU time (the sum of the tms_stime and tms_cstime values in a struct
19 tms as returned by times(2)).
20 Note: some shells (e.g., bash(1)) have a built-in time command that
22 provides less functionality than the command described here. To access
23 the real command, you may need to specify its pathname (something like
24 /usr/bin/time).
25
27 -p When in the POSIX locale, use the precise traditional format
28 "real %f\nuser %f\nsys %f\n"
30 (with numbers in seconds) where the number of decimals in the
32 output for %f is unspecified but is sufficient to express the
33 clock tick accuracy, and at least one.
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36 If command was invoked, the exit status is that of command. Otherwise
37 it is 127 if command could not be found, 126 if it could be found but
38 could not be invoked, and some other non-zero value (1-125) if some‐
39 thing else went wrong.
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42 The variables LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, LC_NUMERIC, NLSPATH,
43 and PATH are used. The last one to search for command. The remaining
44 ones for the text and formatting of the output.
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47 Below a description of the GNU 1.7 version of time. Disregarding the
48 name of the utility, GNU makes it output lots of useful information,
49 not only about time used, but also on other resources like memory, I/O
50 and IPC calls (where available). The output is formatted using a for‐
51 mat string that can be specified using the -f option or the TIME envi‐
52 ronment variable.
53 The default format string is:
55 %Uuser %Ssystem %Eelapsed %PCPU (%Xtext+%Ddata %Mmax)k
57 %Iinputs+%Ooutputs (%Fmajor+%Rminor)pagefaults %Wswaps
58 When the -p option is given the (portable) output format
60 real %e
62 user %U
63 sys %S
64 is used.
66 The format string
68 The format is interpreted in the usual printf-like way. Ordinary char‐
69 acters are directly copied, tab, newline and backslash are escaped
70 using \t, \n and \\, a percent sign is represented by %%, and otherwise
71 % indicates a conversion. The program time will always add a trailing
72 newline itself. The conversions follow. All of those used by tcsh(1)
73 are supported.
74 Time
76 %E Elapsed real time (in [hours:]minutes:seconds).
78 %e (Not in tcsh.) Elapsed real time (in seconds).
80 %S Total number of CPU-seconds that the process spent in kernel
82 mode.
83 %U Total number of CPU-seconds that the process spent in user mode.
85 %P Percentage of the CPU that this job got, computed as (%U + %S) /
87 %E.
88 Memory
90 %M Maximum resident set size of the process during its lifetime, in
92 Kbytes.
93 %t (Not in tcsh.) Average resident set size of the process, in
95 Kbytes.
96 %K Average total (data+stack+text) memory use of the process, in
98 Kbytes.
99 %D Average size of the process's unshared data area, in Kbytes.
101 %p (Not in tcsh.) Average size of the process's unshared stack
103 space, in Kbytes.
104 %X Average size of the process's shared text space, in Kbytes.
106 %Z (Not in tcsh.) System's page size, in bytes. This is a per-sys‐
108 tem constant, but varies between systems.
109 %F Number of major page faults that occurred while the process was
111 running. These are faults where the page has to be read in from
112 disk.
113 %R Number of minor, or recoverable, page faults. These are faults
115 for pages that are not valid but which have not yet been claimed
116 by other virtual pages. Thus the data in the page is still
117 valid but the system tables must be updated.
118 %W Number of times the process was swapped out of main memory.
120 %c Number of times the process was context-switched involuntarily
122 (because the time slice expired).
123 %w Number of waits: times that the program was context-switched
125 voluntarily, for instance while waiting for an I/O operation to
126 complete.
127 I/O
129 %I Number of file system inputs by the process.
131 %O Number of file system outputs by the process.
133 %r Number of socket messages received by the process.
135 %s Number of socket messages sent by the process.
137 %k Number of signals delivered to the process.
139 %C (Not in tcsh.) Name and command-line arguments of the command
141 being timed.
142 %x (Not in tcsh.) Exit status of the command.
144 GNU Options
146 -f FORMAT, --format=FORMAT
147 Specify output format, possibly overriding the format specified
148 in the environment variable TIME.
149 -p, --portability
151 Use the portable output format.
152 -o FILE, --output=FILE
154 Do not send the results to stderr, but overwrite the specified
155 file.
156 -a, --append
158 (Used together with -o.) Do not overwrite but append.
159 -v, --verbose
161 Give very verbose output about all the program knows about.
162 GNU Standard Options
164 --help Print a usage message on standard output and exit successfully.
165 -V, --version
167 Print version information on standard output, then exit success‐
168 fully.
169 -- Terminate option list.
171
173 Not all resources are measured by all versions of Unix, so some of the
174 values might be reported as zero. The present selection was mostly
175 inspired by the data provided by 4.2 or 4.3BSD.
176 GNU time version 1.7 is not yet localized. Thus, it does not implement
178 the POSIX requirements.
179 The environment variable TIME was badly chosen. It is not unusual for
181 systems like autoconf(1) or make(1) to use environment variables with
182 the name of a utility to override the utility to be used. Uses like
183 MORE or TIME for options to programs (instead of program pathnames)
184 tend to lead to difficulties.
185 It seems unfortunate that -o overwrites instead of appends. (That is,
187 the -a option should be the default.)
188 Mail suggestions and bug reports for GNU time to
190 bug-utils@prep.ai.mit.edu
191 Please include the version of time, which you can get by running
192 time --version
193 and the operating system and C compiler you used.
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196 tcsh(1), times(2), wait3(2)
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199 This page is part of release 3.22 of the Linux man-pages project. A
200 description of the project, and information about reporting bugs, can
201 be found at http://www.kernel.org/doc/man-pages/.
202 2008-11-14 TIME(1)