bsd/man/man2/getpriority.2

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  34 .\"     @(#)getpriority.2       8.1 (Berkeley) 6/4/93
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  36 .Dd June 4, 1993
  37 .Dt GETPRIORITY 2
  38 .Os BSD 4
  39 .Sh NAME
  40 .Nm getpriority ,
  41 .Nm setpriority
  42 .Nd get/set program scheduling priority
  43 .Sh SYNOPSIS
  44 .Fd #include <sys/time.h>
  45 .Fd #include <sys/resource.h>
  46 .Ft int
  47 .Fn getpriority "int which" "int who"
  48 .Ft int
  49 .Fn setpriority "int which" "int who" "int prio"
  50 .Sh DESCRIPTION
  51 The scheduling
  52 priority of the process, process group, or user, as indicated by
  53 .Fa which
  54 and
  55 .Fa who
  56 is obtained with the
  57 .Fn getpriority
  58 call and set with the
  59 .Fn setpriority
  60 call.
  61 .Fa Which
  62 is one of
  63 .Dv PRIO_PROCESS ,
  64 .Dv PRIO_PGRP ,
  65 or
  66 .Dv PRIO_USER ,
  67 and
  68 .Fa who
  69 is interpreted relative to
  70 .Fa which
  71 (a process identifier for
  72 .Dv PRIO_PROCESS ,
  73 process group
  74 identifier for
  75 .Dv PRIO_PGRP ,
  76 and a user ID for
  77 .Dv PRIO_USER ) .
  78 A zero value of
  79 .Fa who
  80 denotes the current process, process group, or user.
  81 .Fa Prio
  82 is a value in the range -20 to 20.  The default priority is 0;
  83 lower priorities cause more favorable scheduling.
  84 .Pp
  85 The
  86 .Fn getpriority
  87 call returns the highest priority (lowest numerical value)
  88 enjoyed by any of the specified processes.  The
  89 .Fn setpriority
  90 call sets the priorities of all of the specified processes
  91 to the specified value.  Only the super-user may lower priorities.
  92 .Sh RETURN VALUES
  93 Since
  94 .Fn getpriority
  95 can legitimately return the value -1, it is necessary
  96 to clear the external variable
  97 .Va errno
  98 prior to the
  99 call, then check it afterward to determine
 100 if a -1 is an error or a legitimate value.
 101 The
 102 .Fn setpriority
 103 call returns 0 if there is no error, or
 104 -1 if there is.
 105 .Sh ERRORS
 106 .Fn Getpriority
 107 and
 108 .Fn setpriority
 109 will fail if:
 110 .Bl -tag -width Er
 111 .It Bq Er ESRCH
 112 No process was located using the
 113 .Fa which
 114 and
 115 .Fa who
 116 values specified.
 117 .It Bq Er EINVAL
 118 .Fa Which
 119 was not one of
 120 .Dv PRIO_PROCESS ,
 121 .Dv PRIO_PGRP ,
 122 or
 123 .Dv PRIO_USER .
 124 .El
 125 .Pp
 126 .Bl -tag -width Er
 127 In addition to the errors indicated above,
 128 .Fn setpriority
 129 will fail if:
 130 .It Bq Er EPERM
 131 A process was located, but neither its effective nor real user
 132 ID matched the effective user ID of the caller.
 133 .It Bq Er EACCES
 134 A non super-user attempted to lower a process priority.
 135 .El
 136 .Sh SEE ALSO
 137 .Xr nice 1 ,
 138 .Xr fork 2 ,
 139 .Xr renice 8
 140 .Sh HISTORY
 141 The
 142 .Fn getpriority
 143 function call appeared in
 144 .Bx 4.2 .