Detailed explanation of the use of Linux time command

time [options] command [arguments...]

-f FORMAT, --format=FORMAT: Output using the specified format. If the output format is not specified, the format specified by the environment variable TIME is used. -p, --portability: Use a compatible output format, real %e user %U sys %S. The purpose of this is to be compatible with the POSIX specification. -o FILE, --output=FILE: Set the result output file. This option will write the output of time to the specified file. If the file already exists, overwrite its contents -a, --append: Used with the -o option, use append mode to write the output to the specified file -v, --verbose: Use verbose mode to output statistics as much as possible --help: Display help information -V, --version: Display version information -- : Terminate the option list

Time
%E: The time it takes to execute the command, in the format [hours:]minutes:seconds
%e: The time it takes to execute the instruction, in seconds %S: The time it takes in kernel mode when the instruction is executed, in seconds %U: The time it takes in user mode when the instruction is executed, in seconds %P: The percentage of CPU usage when executing the instruction. In fact, this number is the CPU time in kernel mode plus user mode divided by the total time ((%S+%U)/%E)

Memory
%M: The maximum amount of memory used during execution. Unit: KB
%t: The average memory usage during execution, in KB
%K: The average size of the total memory (stack+data+text) used by the executed program, in KB
%D: The average size of the unshared data area of ​​the executing program, in KB
%p: The average size of the unshared stack of the executing program, in KB
%X: The average value of the shared text segment of the executing program, in KB
%Z: The size of the system memory page, in bytes. This is a constant for the same system %F: Number of memory page faults. Memory page faults refer to the need to read data from disk into memory %R: The number of minor or recoverable page faults. These are faults for invalid pages, but that memory page is not yet in use by other virtual pages. Therefore, the data in the page is still valid, but the system table must be updated %W: The number of times the process has been swapped out of memory %c: The number of times the process context has been switched (because the time slice has expired)
%w: The number of times the process waits, which refers to the number of times the program actively switches contexts, such as waiting for an I/O operation to complete.
%I: The number of files input by this program %O: The number of files output by this program %r: The number of Socket Messages received by this program
%s: Socket Message sent by this program
%k: The number of signals received by this program Command Info
%C: Parameters and command name during execution %x: Exit Status of the command

time date 
Fri May 31 11:30:04 CST 2019

real 0m0.001s
user 0m0.000s
sys 0m0.000s