Question

Just a little question about timing programs on Linux: the time command allows to
measure the execution time of a program:

[ed@lbox200 ~]$ time sleep 1

real    0m1.004s
user    0m0.000s
sys     0m0.004s

Which works fine. But if I try to redirect the output to a file, it fails.

[ed@lbox200 ~]$ time sleep 1 > time.txt

real    0m1.004s
user    0m0.001s
sys     0m0.004s

[ed@lbox200 ~]$ cat time.txt 
[ed@lbox200 ~]$ 

I know there are other implementations of time with the option -o to write a file but
my question is about the command without those options.

Any suggestions ?

Answer 1

Try

{ time sleep 1 ; } 2> time.txt

which combines the STDERR of “time” and your command into time.txt

Or use

{ time sleep 1 2> sleep.stderr ; } 2> time.txt

which puts STDERR from “sleep” into the file “sleep.stderr” and only STDERR from “time” goes into “time.txt”