nice: Run a command with modified niceness
nice prints a process’s niceness, or runs
a command with modified niceness. niceness affects how
favorably the process is scheduled in the system.
nice [option]… [command [arg]…]
If no arguments are given,
nice prints the current niceness.
nice runs the given
command with its
niceness adjusted. By default, its niceness is incremented by 10.
Niceness values range at least from -20 (process has high priority and gets more resources, thus slowing down other processes) through 19 (process has lower priority and runs slowly itself, but has less impact on the speed of other running processes). Some systems may have a wider range of niceness values; conversely, other systems may enforce more restrictive limits. An attempt to set the niceness outside the supported range is treated as an attempt to use the minimum or maximum supported value.
A niceness should not be confused with a scheduling priority, which
lets applications determine the order in which threads are scheduled
to run. Unlike a priority, a niceness is merely advice to the
scheduler, which the scheduler is free to ignore. Also, as a point of
terminology, POSIX defines the behavior of
terms of a nice value, which is the non-negative difference
between a niceness and the minimum niceness. Though
conforms to POSIX, its documentation and diagnostics use the
term “niceness” for compatibility with historical practice.
command must not be a special built-in utility (see Special built-in utilities).
Due to shell aliases and built-in
nice functions, using an
nice interactively or in a script may get you
different functionality than that described here. Invoke it via
env nice …) to avoid interference
from the shell.
Note to change the niceness of an existing process,
one needs to use the
The program accepts the following option. Also see Common options. Options must precede operands.
adjustment instead of 10 to the command’s niceness. If
adjustment is negative and you lack appropriate privileges,
nice issues a warning but otherwise acts as if you specified
a zero adjustment.
nice also supports an obsolete
-adjustment. New scripts should use
-n adjustment instead.
nice is installed only on systems that have the POSIX
setpriority function, so portable scripts should not rely on
its existence on non-POSIX platforms.
0 if no command is specified and the niceness is output 125 if nice itself fails 126 if command is found but cannot be invoked 127 if command cannot be found the exit status of command otherwise
It is sometimes useful to run a non-interactive program with reduced niceness.
$ nice factor 4611686018427387903
nice prints the current niceness,
you can invoke it through itself to demonstrate how it works.
The default behavior is to increase the niceness by ‘
$ nice 0 $ nice nice 10 $ nice -n 10 nice 10
adjustment is relative to the current niceness. In the
next example, the first
nice invocation runs the second one
with niceness 10, and it in turn runs the final one with a niceness
that is 3 more:
$ nice nice -n 3 nice 13
Specifying a niceness larger than the supported range is the same as specifying the maximum supported value:
$ nice -n 10000000000 nice 19
Only a privileged user may run a process with lower niceness:
$ nice -n -1 nice nice: cannot set niceness: Permission denied 0 $ sudo nice -n -1 nice -1