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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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE

DESCRIPTION

       nice()  adds  inc to the nice value for the calling process.  (A higher nice value means a
       low priority.)  Only the superuser may specify a negative increment, or priority increase.
       The range for nice values is described in getpriority(2).

RETURN VALUE

       On  success,  the  new  nice  value  is  returned  (but see NOTES below).  On error, -1 is
       returned, and errno is set appropriately.

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

       SVr4,  4.3BSD,  POSIX.1-2001.   However,  the Linux and (g)libc (earlier than glibc 2.2.4)
       return value is nonstandard, see below.  SVr4 documents an additional EINVAL error code.

NOTES

       SUSv2 and POSIX.1-2001 specify that nice() should return the new nice value.  However, the
       Linux  syscall  and  the  nice()  library  function  provided in older versions of (g)libc
       (earlier than glibc 2.2.4) return 0 on success.  The new nice value  can  be  found  using
       getpriority(2).

       Since  glibc  2.2.4, nice() is implemented as a library function that calls getpriority(2)
       to obtain the new nice value to be returned to the caller.  With  this  implementation,  a
       successful  call  can legitimately return -1.  To reliably detect an error, set errno to 0
       before the call, and check its value when nice() returns -1.

SEE ALSO

       nice(1), renice(1), fork(2), getpriority(2), setpriority(2), capabilities(7)

COLOPHON

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