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nice(3)
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
  increment 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 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)