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1 | .\" Hey Emacs! This file is -*- nroff -*- source. |
| 2 | .\" | |
| 3 | .\" Copyright (c) 1995 Michael Chastain (mec@shell.portal.com), 15 April 1995. | |
| 4 | .\" | |
| 5 | .\" This is free documentation; you can redistribute it and/or | |
| 6 | .\" modify it under the terms of the GNU General Public License as | |
| 7 | .\" published by the Free Software Foundation; either version 2 of | |
| 8 | .\" the License, or (at your option) any later version. | |
| 9 | .\" | |
| 10 | .\" The GNU General Public License's references to "object code" | |
| 11 | .\" and "executables" are to be interpreted as the output of any | |
| 12 | .\" document formatting or typesetting system, including | |
| 13 | .\" intermediate and printed output. | |
| 14 | .\" | |
| 15 | .\" This manual is distributed in the hope that it will be useful, | |
| 16 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 17 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 18 | .\" GNU General Public License for more details. | |
| 19 | .\" | |
| 20 | .\" You should have received a copy of the GNU General Public | |
| 21 | .\" License along with this manual; if not, write to the Free | |
| 22 | .\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, | |
| 23 | .\" USA. | |
| 24 | .\" | |
| 25 | .\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com> | |
| 26 | .\" Modified 1997-07-30 by Paul Slootman <paul@wurtel.demon.nl> | |
| 27 | .\" Modified 2004-05-27 by Michael Kerrisk <mtk16@ext.canterbury.ac.nz> | |
| 28 | .\" | |
| 29 | .TH ADJTIMEX 2 2004-05-27 "Linux 2.6.6" "Linux Programmer's Manual" | |
| 30 | .SH NAME | |
| 31 | adjtimex \- tune kernel clock | |
| 32 | .SH SYNOPSIS | |
| 33 | .B #include <sys/timex.h> | |
| 34 | .sp | |
| 35 | .BI "int adjtimex(struct timex *" "buf" ); | |
| 36 | .SH DESCRIPTION | |
| 37 | Linux uses David L. Mills' clock adjustment algorithm (see RFC 1305). | |
| 38 | The system call | |
| 39 | .B adjtimex | |
| 40 | reads and optionally sets adjustment parameters for this algorithm. | |
| 41 | It takes a pointer to a | |
| 42 | .I timex | |
| 43 | structure, updates kernel parameters from field values, | |
| 44 | and returns the same structure with current kernel values. | |
| 45 | This structure is declared as follows: | |
| 46 | .PP | |
| 47 | .RS | |
| 48 | .nf | |
| 49 | struct timex { | |
| 50 | int modes; /* mode selector */ | |
| 51 | long offset; /* time offset (usec) */ | |
| 52 | long freq; /* frequency offset (scaled ppm) */ | |
| 53 | long maxerror; /* maximum error (usec) */ | |
| 54 | long esterror; /* estimated error (usec) */ | |
| 55 | int status; /* clock command/status */ | |
| 56 | long constant; /* pll time constant */ | |
| 57 | long precision; /* clock precision (usec) (read only) */ | |
| 58 | long tolerance; /* clock frequency tolerance (ppm) | |
| 59 | (read only) */ | |
| 60 | struct timeval time; /* current time (read only) */ | |
| 61 | long tick; /* usecs between clock ticks */ | |
| 62 | }; | |
| 63 | .fi | |
| 64 | .RE | |
| 65 | .PP | |
| 66 | The | |
| 67 | .I modes | |
| 68 | field determines which parameters, if any, to set. | |
| 69 | It may contain a | |
| 70 | .RI bitwise- or | |
| 71 | combination of zero or more of the following bits: | |
| 72 | .PP | |
| 73 | .RS | |
| 74 | .nf | |
| 75 | #define ADJ_OFFSET 0x0001 /* time offset */ | |
| 76 | #define ADJ_FREQUENCY 0x0002 /* frequency offset */ | |
| 77 | #define ADJ_MAXERROR 0x0004 /* maximum time error */ | |
| 78 | #define ADJ_ESTERROR 0x0008 /* estimated time error */ | |
| 79 | #define ADJ_STATUS 0x0010 /* clock status */ | |
| 80 | #define ADJ_TIMECONST 0x0020 /* pll time constant */ | |
| 81 | #define ADJ_TICK 0x4000 /* tick value */ | |
| 82 | #define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime */ | |
| 83 | .fi | |
| 84 | .RE | |
| 85 | .PP | |
| 86 | Ordinary users are restricted to a zero value for | |
| 87 | .IR mode . | |
| 88 | Only the superuser may set any parameters. | |
| 89 | .br | |
| 90 | .ne 12v | |
| 91 | .SH "RETURN VALUE" | |
| 92 | On success, | |
| 93 | .B adjtimex | |
| 94 | returns the clock state: | |
| 95 | .PP | |
| 96 | .RS | |
| 97 | .nf | |
| 98 | #define TIME_OK 0 /* clock synchronized */ | |
| 99 | #define TIME_INS 1 /* insert leap second */ | |
| 100 | #define TIME_DEL 2 /* delete leap second */ | |
| 101 | #define TIME_OOP 3 /* leap second in progress */ | |
| 102 | #define TIME_WAIT 4 /* leap second has occurred */ | |
| 103 | #define TIME_BAD 5 /* clock not synchronized */ | |
| 104 | .fi | |
| 105 | .RE | |
| 106 | .PP | |
| 107 | On failure, | |
| 108 | .B adjtimex | |
| 109 | returns \-1 and sets | |
| 110 | .IR errno . | |
| 111 | .SH ERRORS | |
| 112 | .TP | |
| 113 | .B EFAULT | |
| 114 | .I buf | |
| 115 | does not point to writable memory. | |
| 116 | .TP | |
| 117 | .B EINVAL | |
| 118 | An attempt is made to set | |
| 119 | .I buf.offset | |
| 120 | to a value outside the range \-131071 to +131071, | |
| 121 | or to set | |
| 122 | .I buf.status | |
| 123 | to a value other than those listed above, | |
| 124 | or to set | |
| 125 | .I buf.tick | |
| 126 | to a value outside the range | |
| 127 | .RB 900000/ HZ | |
| 128 | to | |
| 129 | .RB 1100000/ HZ , | |
| 130 | where | |
| 131 | .B HZ | |
| 132 | is the system timer interrupt frequency. | |
| 133 | .TP | |
| 134 | .B EPERM | |
| 135 | .I buf.mode | |
| 136 | is non-zero and the caller does not have sufficient privilege. | |
| 137 | Under Linux the | |
| 138 | .B CAP_SYS_TIME | |
| 139 | capability is required. | |
| 140 | .SH "CONFORMING TO" | |
| 141 | \fBadjtimex\fP is Linux specific and should not be used in programs | |
| 142 | intended to be portable. There is a similar but less general call | |
| 143 | \fBadjtime\fR in SVr4. | |
| 144 | .SH "SEE ALSO" | |
| 145 | .BR settimeofday (2), | |
| 146 | .BR capabilities (7) |