NAME

nice − Changes the scheduling priority of a process

LIBRARY

Standard C Library (libc.a, libc.so)
Berkeley Compatibility Library (libbsd.a)

SYNOPSIS

#include <unistd.h>

int nice(
int increment);

STANDARDS

Interfaces documented on this reference page conform to industry standards as follows:

nice():  XPG4, XPG4−UNIX

Refer to the standards(5) reference page for more information about industry standards and associated tags. 

PARAMETERS

incrementSpecifies 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 nonnegative 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). 

[Digital]  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-compatible 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:

[EPERM]The calling process does not have appropriate privilege. 

[Digital]  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)