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nice(3) [osf1 man page]

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)

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nice(2) 							   System Calls 							   nice(2)

NAME
nice - change priority of a process SYNOPSIS
#include <unistd.h> int nice(int incr); DESCRIPTION
The nice() function allows a process to change its priority. The invoking process must be in a scheduling class that supports the nice(). The nice() function adds the value of incr to the nice value of the calling process. A process's nice value is a non-negative number for which a greater positive value results in lower CPU priority. A maximum nice value of (2 * NZERO) -1 and a minimum nice value of 0 are imposed by the system. NZERO is defined in <limits.h> with a default value of 20. Requests for values above or below these limits result in the nice value being set to the corresponding limit. A nice value of 40 is treated as 39. Calling the nice() function has no effect on the priority of processes or threads with policy SCHED_FIFO or SCHED_RR. Only a process with the {PRIV_PROC_PRIOCNTL} privilege can lower the nice value. RETURN VALUES
Upon successful completion, nice() returns the new nice value minus NZERO. Otherwise, -1 is returned, the process's nice value is not changed, and errno is set to indicate the error. ERRORS
The nice() function will fail if: EINVAL The nice() function is called by a process in a scheduling class other than time-sharing or fixed-priority. EPERM The incr argument is negative or greater than 40 and the {PRIV_PROC_PRIOCNTL} privilege is not asserted in the effective set of the calling process. USAGE
The priocntl(2) function is a more general interface to scheduler functions. Since -1 is a permissible return value in a successful situation, an application wishing to check for error situations should set errno to 0, then call nice(), and if it returns -1, check to see if errno is non-zero. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Async-Signal-Safe | +-----------------------------+-----------------------------+ SEE ALSO
nice(1), exec(2), priocntl(2), getpriority(3C), attributes(5), privileges(5), standards(5) SunOS 5.10 1 Apr 2004 nice(2)

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