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 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. The remaining ones for the text and for‐
45 matting of the output.
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48 Below a description of the GNU 1.7 version of time. Disregarding the
49 name of the utility, GNU makes it output lots of useful information,
50 not only about time used, but also on other resources like memory, I/O
51 and IPC calls (where available). The output is formatted using a for‐
52 mat string that can be specified using the -f option or the TIME envi‐
53 ronment variable.
54 The default format string is:
56 %Uuser %Ssystem %Eelapsed %PCPU (%Xtext+%Ddata %Mmax)k
58 %Iinputs+%Ooutputs (%Fmajor+%Rminor)pagefaults %Wswaps
59 When the -p option is given, the (portable) output format is used:
61 real %e
63 user %U
64 sys %S
65 The format string
67 The format is interpreted in the usual printf-like way. Ordinary char‐
68 acters are directly copied, tab, newline and backslash are escaped
69 using \t, \n and \\, a percent sign is represented by %%, and otherwise
70 % indicates a conversion. The program time will always add a trailing
71 newline itself. The conversions follow. All of those used by tcsh(1)
72 are supported.
73 Time
75 %E Elapsed real time (in [hours:]minutes:seconds).
77 %e (Not in tcsh(1).) Elapsed real time (in seconds).
79 %S Total number of CPU-seconds that the process spent in kernel
81 mode.
82 %U Total number of CPU-seconds that the process spent in user mode.
84 %P Percentage of the CPU that this job got, computed as (%U + %S) /
86 %E.
87 Memory
89 %M Maximum resident set size of the process during its lifetime, in
91 Kbytes.
92 %t (Not in tcsh(1).) Average resident set size of the process, in
94 Kbytes.
95 %K Average total (data+stack+text) memory use of the process, in
97 Kbytes.
98 %D Average size of the process's unshared data area, in Kbytes.
100 %p (Not in tcsh(1).) Average size of the process's unshared stack
102 space, in Kbytes.
103 %X Average size of the process's shared text space, in Kbytes.
105 %Z (Not in tcsh(1).) System's page size, in bytes. This is a per-
107 system constant, but varies between systems.
108 %F Number of major page faults that occurred while the process was
110 running. These are faults where the page has to be read in from
111 disk.
112 %R Number of minor, or recoverable, page faults. These are faults
114 for pages that are not valid but which have not yet been claimed
115 by other virtual pages. Thus the data in the page is still
116 valid but the system tables must be updated.
117 %W Number of times the process was swapped out of main memory.
119 %c Number of times the process was context-switched involuntarily
121 (because the time slice expired).
122 %w Number of waits: times that the program was context-switched
124 voluntarily, for instance while waiting for an I/O operation to
125 complete.
126 I/O
128 %I Number of filesystem inputs by the process.
130 %O Number of filesystem outputs by the process.
132 %r Number of socket messages received by the process.
134 %s Number of socket messages sent by the process.
136 %k Number of signals delivered to the process.
138 %C (Not in tcsh(1).) Name and command-line arguments of the com‐
140 mand being timed.
141 %x (Not in tcsh(1).) Exit status of the command.
143 GNU options
145 -f format, --format=format
146 Specify output format, possibly overriding the format specified
147 in the environment variable TIME.
148 -p, --portability
150 Use the portable output format.
151 -o file, --output=file
153 Do not send the results to stderr, but overwrite the specified
154 file.
155 -a, --append
157 (Used together with -o.) Do not overwrite but append.
158 -v, --verbose
160 Give very verbose output about all the program knows about.
161 GNU standard options
163 --help Print a usage message on standard output and exit successfully.
164 -V, --version
166 Print version information on standard output, then exit success‐
167 fully.
168 -- Terminate option list.
170
172 Not all resources are measured by all versions of UNIX, so some of the
173 values might be reported as zero. The present selection was mostly
174 inspired by the data provided by 4.2 or 4.3BSD.
175 GNU time version 1.7 is not yet localized. Thus, it does not implement
177 the POSIX requirements.
178 The environment variable TIME was badly chosen. It is not unusual for
180 systems like autoconf(1) or make(1) to use environment variables with
181 the name of a utility to override the utility to be used. Uses like
182 MORE or TIME for options to programs (instead of program pathnames)
183 tend to lead to difficulties.
184 It seems unfortunate that -o overwrites instead of appends. (That is,
186 the -a option should be the default.)
187 Mail suggestions and bug reports for GNU time to
189 bug-utils@prep.ai.mit.edu. Please include the version of time, which
190 you can get by running
191 time --version
193 and the operating system and C compiler you used.
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197 bash(1), tcsh(1), times(2), wait3(2)
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200 This page is part of release 4.15 of the Linux man-pages project. A
201 description of the project, information about reporting bugs, and the
202 latest version of this page, can be found at
203 https://www.kernel.org/doc/man-pages/.
204 2017-09-15 TIME(1)