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 ar‐
13 guments. When command finishes, time writes a message to standard er‐
14 ror giving timing statistics about this program run. These statistics
15 consist of (i) the elapsed real time between invocation and termina‐
16 tion, (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 similar information on the usage of time and possibly other
23 resources. To access the real command, you may need to specify its
24 pathname (something like /usr/bin/time).
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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 nonzero value (1–125) if something
39 else went wrong.
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42 The variables LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, LC_NUMERIC, and
43 NLSPATH are used for the text and formatting of the output. PATH is
44 used to search for command.
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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 is used:
60 real %e
62 user %U
63 sys %S
64 The format string
66 The format is interpreted in the usual printf-like way. Ordinary char‐
67 acters are directly copied, tab, newline, and backslash are escaped us‐
68 ing \t, \n, and \\, a percent sign is represented by %%, and otherwise
69 % indicates a conversion. The program time will always add a trailing
70 newline itself. The conversions follow. All of those used by tcsh(1)
71 are supported.
72 Time
74 %E Elapsed real time (in [hours:]minutes:seconds).
76 %e (Not in tcsh(1).) Elapsed real time (in seconds).
78 %S Total number of CPU-seconds that the process spent in kernel
80 mode.
81 %U Total number of CPU-seconds that the process spent in user mode.
83 %P Percentage of the CPU that this job got, computed as (%U + %S) /
85 %E.
86 Memory
88 %M Maximum resident set size of the process during its lifetime, in
90 Kbytes.
91 %t (Not in tcsh(1).) Average resident set size of the process, in
93 Kbytes.
94 %K Average total (data+stack+text) memory use of the process, in
96 Kbytes.
97 %D Average size of the process's unshared data area, in Kbytes.
99 %p (Not in tcsh(1).) Average size of the process's unshared stack
101 space, in Kbytes.
102 %X Average size of the process's shared text space, in Kbytes.
104 %Z (Not in tcsh(1).) System's page size, in bytes. This is a per-
106 system constant, but varies between systems.
107 %F Number of major page faults that occurred while the process was
109 running. These are faults where the page has to be read in from
110 disk.
111 %R Number of minor, or recoverable, page faults. These are faults
113 for pages that are not valid but which have not yet been claimed
114 by other virtual pages. Thus the data in the page is still
115 valid but the system tables must be updated.
116 %W Number of times the process was swapped out of main memory.
118 %c Number of times the process was context-switched involuntarily
120 (because the time slice expired).
121 %w Number of waits: times that the program was context-switched
123 voluntarily, for instance while waiting for an I/O operation to
124 complete.
125 I/O
127 %I Number of filesystem inputs by the process.
129 %O Number of filesystem outputs by the process.
131 %r Number of socket messages received by the process.
133 %s Number of socket messages sent by the process.
135 %k Number of signals delivered to the process.
137 %C (Not in tcsh(1).) Name and command-line arguments of the com‐
139 mand being timed.
140 %x (Not in tcsh(1).) Exit status of the command.
142 GNU options
144 -f format, --format=format
145 Specify output format, possibly overriding the format specified
146 in the environment variable TIME.
147 -p, --portability
149 Use the portable output format.
150 -o file, --output=file
152 Do not send the results to stderr, but overwrite the specified
153 file.
154 -a, --append
156 (Used together with -o.) Do not overwrite but append.
157 -v, --verbose
159 Give very verbose output about all the program knows about.
160 -q, --quiet
162 Don't report abnormal program termination (where command is ter‐
163 minated by a signal) or nonzero exit status.
164 GNU standard options
166 --help Print a usage message on standard output and exit successfully.
167 -V, --version
169 Print version information on standard output, then exit success‐
170 fully.
171 -- Terminate option list.
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175 Not all resources are measured by all versions of UNIX, so some of the
176 values might be reported as zero. The present selection was mostly in‐
177 spired by the data provided by 4.2 or 4.3BSD.
178 GNU time version 1.7 is not yet localized. Thus, it does not implement
180 the POSIX requirements.
181 The environment variable TIME was badly chosen. It is not unusual for
183 systems like autoconf(1) or make(1) to use environment variables with
184 the name of a utility to override the utility to be used. Uses like
185 MORE or TIME for options to programs (instead of program pathnames)
186 tend to lead to difficulties.
187 It seems unfortunate that -o overwrites instead of appends. (That is,
189 the -a option should be the default.)
190 Mail suggestions and bug reports for GNU time to bug-time@gnu.org.
192 Please include the version of time, which you can get by running
193 time --version
195 and the operating system and C compiler you used.
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199 bash(1), tcsh(1), times(2), wait3(2)
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202 This page is part of release 5.13 of the Linux man-pages project. A
203 description of the project, information about reporting bugs, and the
204 latest version of this page, can be found at
205 https://www.kernel.org/doc/man-pages/.
206 2019-03-06 TIME(1)