NICE
Section: Linux Programmer's Manual (2)
Updated: 2021-03-22
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NAME
nice - change process priority
SYNOPSIS
#include <unistd.h>
int nice(int inc);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
nice():
_XOPEN_SOURCE
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
nice()
adds
inc
to the nice value for the calling thread.
(A higher nice value means a lower priority.)
The range of the nice value is +19 (low priority) to -20 (high priority).
Attempts to set a nice value outside the range are clamped to the range.
Traditionally, only a privileged process could lower the nice value
(i.e., set a higher priority).
However, since Linux 2.6.12, an unprivileged process can decrease
the nice value of a target process that has a suitable
RLIMIT_NICE
soft limit; see
getrlimit(2)
for details.
RETURN VALUE
On success, the new nice value is returned (but see NOTES below).
On error, -1 is returned, and
errno
is set to indicate the error.
A successful call can legitimately return -1.
To detect an error, set
errno
to 0 before the call, and check whether it is nonzero after
nice()
returns -1.
ERRORS
- EPERM
-
The calling process attempted to increase its priority by
supplying a negative
inc
but has insufficient privileges.
Under Linux, the
CAP_SYS_NICE
capability is required.
(But see the discussion of the
RLIMIT_NICE
resource limit in
setrlimit(2).)
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
However, the raw system call and (g)libc
(earlier than glibc 2.2.4) return value is nonstandard, see below.
NOTES
For further details on the nice value, see
sched(7).
Note:
the addition of the "autogroup" feature in Linux 2.6.38 means that
the nice value no longer has its traditional effect in many circumstances.
For details, see
sched(7).
C library/kernel differences
POSIX.1 specifies that
nice()
should return the new nice value.
However, the raw Linux system call returns 0 on success.
Likewise, the
nice()
wrapper function provided in glibc 2.2.3 and earlier returns 0 on success.
Since glibc 2.2.4, the
nice()
wrapper function provided by glibc provides conformance to POSIX.1 by calling
getpriority(2)
to obtain the new nice value, which is then returned to the caller.
SEE ALSO
nice(1),
renice(1),
fork(2),
getpriority(2),
getrlimit(2),
setpriority(2),
capabilities(7),
sched(7)
COLOPHON
This page is part of release 5.11 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- C library/kernel differences
-
- SEE ALSO
-
- COLOPHON
-
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Time: 06:22:43 GMT, May 09, 2021