nice(3) Library Functions Manual nice(3)
NAME
nice - Changes the scheduling priority of a process
LIBRARY
Standard C Library (libc) Berkeley Compatibility Library (libbsd)
SYNOPSIS
#include <unistd.h>
int nice( int increment);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
nice(): XSH4.2
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Specifies a value that is added to the current process priority. You can specify a negative value.
DESCRIPTION
The nice() function adds the value specified in the increment parameter to the nice value of the calling process. The nice value is a non-
negative number; a higher nice value gives the process a lower CPU priority.
When you are using the Standard C Library version of the nice() function, the maximum nice value for a process is 39 (2 * {NZERO} -1) and
the minimum is 0 (zero). Requests for values outside these limits result in the nice value being set to the corresponding limit.
[XPG4-UNIX] If execution of the Standard C Library nice() function fails, the system does not alter the specified priority.
Any process can lower its priority (numerically raise its nice value). A process must have superuser privileges to raise its priority
(numerically lower its nice value).
[Tru64 UNIX] For backward compatibility, a version of the nice() function is supported that allows nice values in the range of -20 to 20.
Requests for values above or below these limits result in the nice value being set to the corresponding limit. To use the backward-compat-
ible version of nice(), compile with the Berkeley Compatibility Library (libbsd.a).
RETURN VALUES
Upon successful completion, the nice() function returns the new nice value minus 20 ({NZERO}). Otherwise, the function returns -1 and sets
errno to indicate the error.
ERRORS
The Standard C Library version of nice() sets errno to the specified values for the following conditions: The calling process does not have
appropriate privilege.
[Tru64 UNIX] The libbsd.a version of nice() sets errno to the same values as the setpriority() function. For information about possible
return values for the setpriority() function, see setpriority(2).
RELATED INFORMATION
Functions: exec(2), getpriority(2), setpriority(2)
Standards: standards(5) delim off
nice(3)
