Print execution time of a shell command

Question

Is is possible to print the execution time of a shell command with following combination   root hostname     command to execute   amp  amp  echo  execution time

User · Answer

In zsh you can use   time       In bash or zsh you can use  command time       These  by different mechanisms  force an external command to be used

User · Answer

time is a built-in command in most shells that writes execution time information to the tty    You could also try something like  start time  date   s   lt command-to-execute gt  end time  date   s  echo execution time was  expr  end time -  start time  s    Or in bash   start time  date   s   lt command-to-execute gt   amp  amp  echo run time is   expr  date   s  -  start time  s

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If I m starting a long-running process like a copy or hash and I want to know later how long it took  I just do this     date  sha1sum reallybigfile txt  date   Which will result in the following output   Tue Jun  2 21 16 03 PDT 2015 5089a8e475cc41b2672982f690e5221469390bc0  reallybigfile txt Tue Jun  2 21 33 54 PDT 2015   Granted  as implemented here it isn t very precise and doesn t calculate the elapsed time  But it s dirt simple and sometimes all you need

User · Answer

Just ps -o etime  -p   lt your process pid gt

User · Answer

For a line-by-line delta measurement  try gnonom   It is a command line utility  a bit like moreutils s ts  to prepend timestamp information to the standard output of another command  Useful for long-running processes where you d like a historical record of what s taking so long  Piping anything to gnomon will prepend a timestamp to each line  indicating how long that line was the last line in the buffer--that is  how long it took the next line to appear  By default  gnomon will display the seconds elapsed between each line  but that is configurable

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Adding to  mob s answer   Appending  N to date   s gives us nanosecond accuracy   start  date   s N   lt command gt  end  date   s N  echo  expr  end -  start

User · Answer

Don t forget that there is a difference between bash s builtin time  which should be called by default when you do time command  and  usr bin time  which should require you to call it by its full path    The builtin time always prints to stderr  but  usr bin time will allow you to send time s output to a specific file  so you do not interfere with the executed command s stderr stream   Also   usr bin time s format is configurable on the command line or by the environment variable TIME  whereas bash s builtin time format is only configured by the TIMEFORMAT environment variable     time factor 1234567889234567891   builtin 1234567889234567891  142662263 8653780357  real    0m3 194s user    0m1 596s sys 0m0 004s    usr bin time factor 1234567889234567891 1234567889234567891  142662263 8653780357 1 54user 0 00system 0 02 69elapsed 57 CPU  0avgtext 0avgdata 0maxresident k 0inputs 0outputs  0major 215minor pagefaults 0swaps    usr bin time -o timed factor 1234567889234567891   log to file  timed  1234567889234567891  142662263 8653780357   cat timed 1 56user 0 02system 0 02 49elapsed 63 CPU  0avgtext 0avgdata 0maxresident k 0inputs 0outputs  0major 217minor pagefaults 0swaps

User · Answer

root hostname    time  command    It also distinguishes between real time used and system time used

[shell] Print execution time of a shell command

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