There are three distinct versions of time: it is built in to the C shell, and is an executable program available in /usr/bin/time and /usr/5bin/time when using the Bourne shell. In each case, times are displayed on the diagnostic output stream.
In the case of the C shell, a time command with no command argument simply displays a summary of time used by this shell and its children. When arguments are given the specified simple command is timed and the C shell displays a time summary as described in csh.1
The time commands in /usr/bin/time and /usr/5bin/time time the given command, which must be specified, that is, command is not optional as it is in the C shell's timing facility. When the command is complete, time displays the elapsed time during the command, the time spent in the system, and the time spent in execution of the command. Times are reported in seconds. The only difference between the versions in /usr/bin/time and /usr/5bin/time is between their output formats; /usr/bin/time prints all three times on the same line, while /usr/5bin/time prints them on separate lines.
The three examples here show the differences between the csh version of time and the versions in /usr/bin/time and /usr/bin/time. The example assumes that csh is the shell in use.
example% time wc /usr/share/man/man1/csh.1 1876 11223 65895 /usr/share/man/man1/csh.1 2.7u 0.9s 0:03 91% 3+5k 19+2io 1pf+0w example%/usr/bin/time wc /usr/share/man/man1/csh.1 1876 11223 65895 /usr/share/man/man1/csh.1 4.3 real 2.7 user 1.0 sys example% /usr/5bin/time wc /usr/share/man/man1/csh.1 1876 11223 65895 /usr/share/man/man1/csh.1 real 4.3 user 2.7 sys 1.0 example%
Elapsed time is accurate to the second, while the CPU times are measured to the 50th second. Thus the sum of the CPU times can be up to a second larger than the elapsed time.
When the command being timed is interrupted, the timing values displayed may not always be accurate.
Created by unroff & hp-tools. © by Hans-Peter Bischof. All Rights Reserved (1997).
Last modified 21/April/97