I want to measure execution time of commands and get (to me) strange behavior of the time command.I call time like it is mentioned in the examples of the manpages with the -f or --format option and get a command not found error. Seems like it thinks -f is the command to measure the execution time of...user@laptop:~$ time -f '%e' sleep 1-f: Befehl nicht gefunden.Then I call the same line again, just that I specify the path to time. Result changes, works as intended (wtf?):user@laptop:~$ /usr/bin/time -f '%e' sleep 11.00Now I'm confused... even which can't help me:user@pc:~$ which time/usr/bin/timeAnd... if I don't use options it works fine, even without full path:user@laptop:~$ time sleep 1real    0m1.003suser    0m0.001ssys 0m0.002sHow do I use this command correctly if I want to specify options?Using the full path seems to work, but looks more like an unreliable side effect of something buggy (or something I don't understand)?Edit: I'm using Ubuntu 14.04 LTS (trusty)
call `time` with format option
linux;time
Bash has a built in command called time. So if you just type time it will use the shell built-in which has no options like -f. But man time (which talks about -f) will give the manpage of the /usr/bin/time program. So if you want to use options described in the manpage you should ensure you call the program, not the shell built-in. One way achieving this is using the full path.(IMHO, this is really ugly in bash)For more info, see the links below the question.