diff options
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | manual/sysinfo.texi | 2 | ||||
| -rw-r--r-- | manual/time.texi | 541 |
3 files changed, 345 insertions, 204 deletions
@@ -1,5 +1,11 @@ 2000-04-21 Ulrich Drepper <drepper@redhat.com> + * manual/sysinfo.texi: Fix typo. + * manual/time.texi: Document timelocal, timegm, adjtimex, and stime. + Replace "high precision time" with "high accuracy clock". + Fix language. + Patches by Bryan Henderson <bryanh@giraffe-data.com>. + * nis/nis_findserv.c (__nis_findfastest): Improve memory handling. * nis/nis_print_group_entry.c (nis_print_group_entry): Use alloca instead of malloc. diff --git a/manual/sysinfo.texi b/manual/sysinfo.texi index 54f4985..a8113e1 100644 --- a/manual/sysinfo.texi +++ b/manual/sysinfo.texi @@ -691,7 +691,7 @@ For a remount, @code{mount} ignores @var{fstype}. @c This is traditionally called "rwflag" for historical reasons. @c No point in confusing people today, though. @var{options} specifies a variety of options that apply until the -filesystem in unmounted or remounted. The precise meaning of an option +filesystem is unmounted or remounted. The precise meaning of an option depends on the filesystem and with some filesystems, an option may have no effect at all. Furthermore, for some filesystems, some of these options (but never @code{MS_RDONLY}) can be overridden for individual diff --git a/manual/time.texi b/manual/time.texi index d292d1c..1a1cddd 100644 --- a/manual/time.texi +++ b/manual/time.texi @@ -25,8 +25,6 @@ an Alarm}. @menu * Processor Time:: Measures processor time used by a program. * Calendar Time:: Manipulation of ``real'' dates and times. -* Precision Time:: Manipulation and monitoring of high accuracy - time. * Setting an Alarm:: Sending a signal after a specified time. * Sleeping:: Waiting for a period of time. @end menu @@ -195,42 +193,45 @@ the @code{tms_utime} and @code{tms_stime} fields returned by @node Calendar Time @section Calendar Time -This section describes facilities for keeping track of dates and times -according to the Gregorian calendar. -@cindex Gregorian calendar +This section describes facilities for keeping track of points in time. +This is called calendar time and sometimes absolute time. +@cindex time, absolute @cindex time, calendar @cindex date and time -There are three representations for date and time information: +The GNU C library represents calendar time three ways: @itemize @bullet @item -@dfn{Calendar time} (the @code{time_t} data type) is a compact +@dfn{Simple time} (the @code{time_t} data type) is a compact representation, typically giving the number of seconds elapsed since some implementation-specific base time. -@cindex calendar time +@cindex simple time @item There is also a @dfn{high-resolution time} representation (the @code{struct timeval} data type) that includes fractions of a second. Use this time -representation instead of ordinary calendar time when you need greater +representation instead of simple time when you need greater precision. @cindex high-resolution time @item -@dfn{Local time} or @dfn{broken-down time} (the @code{struct -tm} data type) represents the date and time as a set of components -specifying the year, month, and so on, for a specific time zone. -This time representation is usually used in conjunction with formatting -date and time values. +@dfn{Local time} or @dfn{broken-down time} (the @code{struct tm} data +type) represents the date and time as a set of components specifying the +year, month, and so on in the Gregorian calendar, for a specific time +zone. This time representation is usually used only to communicate with +people. @cindex local time @cindex broken-down time +@cindex Gregorian calendar +@cindex calendar, Gregorian @end itemize @menu * Simple Calendar Time:: Facilities for manipulating calendar time. * High-Resolution Calendar:: A time representation with greater precision. * Broken-down Time:: Facilities for manipulating local time. +* High Accuracy Clock:: Maintaining a high accuracy system clock. * Formatting Date and Time:: Converting times to strings. * Parsing Date and Time:: Convert textual time and date information back into broken-down time values. @@ -243,8 +244,8 @@ date and time values. @node Simple Calendar Time @subsection Simple Calendar Time -This section describes the @code{time_t} data type for representing -calendar time, and the functions which operate on calendar time objects. +This section describes the @code{time_t} data type for representing calendar +time as simple time, and the functions which operate on simple time objects. These facilities are declared in the header file @file{time.h}. @pindex time.h @@ -252,14 +253,19 @@ These facilities are declared in the header file @file{time.h}. @comment time.h @comment ISO @deftp {Data Type} time_t -This is the data type used to represent calendar time. +This is the data type used to represent simple time. Sometimes, it also +represents an elapsed time. When interpreted as an absolute time value, it represents the number of seconds elapsed since 00:00:00 on -January 1, 1970, Coordinated Universal Time. (This date is sometimes +January 1, 1970, Coordinated Universal Time. (This time is sometimes referred to as the @dfn{epoch}.) POSIX requires that this count -ignore leap seconds, but on some hosts this count includes leap seconds +not include leap seconds, but on some hosts this count includes leap seconds if you set @code{TZ} to certain values (@pxref{TZ Variable}). +Note that a simple time has no concept of local time zone. Time @var{N} +is the same instant in time regardless of where on the globe the +computer is. + In the GNU C library, @code{time_t} is equivalent to @code{long int}. In other systems, @code{time_t} might be either an integer or floating-point type. @@ -287,11 +293,36 @@ time value is also stored in @code{*@var{result}}. If the calendar time is not available, the value @w{@code{(time_t)(-1)}} is returned. @end deftypefun +@c The GNU C library implements stime() with a call to settimeofday() on +@c Linux. +@comment time.h +@comment SVID, XPG +@deftypefun int stime (time_t *@var{newtime}) +@code{stime} sets the system clock, i.e. it tells the system that the +present absolute time is @var{newtime}, where @code{newtime} is +interpreted as described in the above definition of @code{time_t}. + +@code{settimeofday} is a newer function which sets the system clock to +better than one second precision. @code{settimeofday} is generally a +better choice than @code{stime}. @xref{High-Resolution Calendar}. + +Only the superuser can set the system clock. + +If the function succeeds, the return value is zero. Otherwise, it is +@code{-1} and @code{errno} is set accordingly: + +@table @code +@item EPERM +The process is not superuser. +@end table +@end deftypefun + + @node High-Resolution Calendar @subsection High-Resolution Calendar -The @code{time_t} data type used to represent calendar times has a +The @code{time_t} data type used to represent simple times has a resolution of only one second. Some applications need more precision. So, the GNU C library also contains functions which are capable of @@ -405,6 +436,22 @@ information is ignored if @var{tzp} is a null pointer. You must be a privileged user in order to use @code{settimeofday}. +Some kernels automatically set the system clock from some source such as +a hardware clock when they start up. Others, including Linux, place the +system clock in an ``invalid'' state (in which attempts to read the time +fail). A call of @code{stime} removes the system clock from an invalid +state, and system startup scripts typically run a program that calls +@code{stime}. + +@code{settimeofday} causes a sudden jump forwards or backwards, which +can cause a variety of problems in a system. Use @code{adjtime} (below) +to make a smooth transition from one time to another by temporarily +speeding up or slowing down the clock. + +With a Linux kernel, @code{adjtimex} does the same thing and can also +make permanent changes to the speed of the system clock so it doesn't +need to be corrected as often. + The return value is @code{0} on success and @code{-1} on failure. The following @code{errno} error conditions are defined for this function: @@ -418,6 +465,7 @@ The operating system does not support setting time zone information, and @end table @end deftypefun +@c On Linux, GNU libc implements adjtime() as a call to adjtimex(). @comment sys/time.h @comment BSD @deftypefun int adjtime (const struct timeval *@var{delta}, struct timeval *@var{olddelta}) @@ -437,6 +485,10 @@ has not yet completed. This function is typically used to synchronize the clocks of computers in a local network. You must be a privileged user to use it. + +With a Linux kernel, you can use the @code{adjtimex} function to +permanently change the clock speed. + The return value is @code{0} on success and @code{-1} on failure. The following @code{errno} error condition is defined for this function: @@ -450,19 +502,32 @@ You do not have privilege to set the time. and @code{adjtime} functions are derived from BSD. +Symbols for the following function are declared in @file{sys/timex.h}. + +@comment sys/timex.h +@comment GNU +@deftypefun int adjtimex (struct timex *@var{timex}) + +@code{adjtimex} is functionally identical to @code{ntp_adjtime}. +@xref{High Accuracy Clock}. + +This function is present only with a Linux kernel. + +@end deftypefun + @node Broken-down Time @subsection Broken-down Time @cindex broken-down time @cindex calendar time and broken-down time -Calendar time is represented as a number of seconds. This is convenient -for calculation, but has no relation to the way people normally -represent dates and times. By contrast, @dfn{broken-down time} is a binary -representation separated into year, month, day, and so on. Broken-down -time values are not useful for calculations, but they are useful for -printing human readable time. +Calendar time is represented as an amount of time since a fixed base +time. This is convenient for calculation, but has no relation to the +way people normally think of dates and times. By contrast, +@dfn{broken-down time} is a binary representation separated into year, +month, day, and so on. Broken-down time values are not useful for +calculations, but they are useful for printing human readable time. -A broken-down time value is always relative to a choice of local time +A broken-down time value is always relative to a choice of time zone, and it also indicates which time zone was used. The symbols in this section are declared in the header file @file{time.h}. @@ -533,7 +598,7 @@ GNU extension, and is not visible in a strict @w{ISO C} environment. @comment time.h @comment ISO @deftypefun {struct tm *} localtime (const time_t *@var{time}) -The @code{localtime} function converts the calendar time pointed to by +The @code{localtime} function converts the simple time pointed to by @var{time} to broken-down time representation, expressed relative to the user's specified time zone. @@ -559,7 +624,7 @@ all threads. POSIX.1c introduced a variant of this function. @comment POSIX.1c @deftypefun {struct tm *} localtime_r (const time_t *@var{time}, struct tm *@var{resultp}) The @code{localtime_r} function works just like the @code{localtime} -function. It takes a pointer to a variable containing the calendar time +function. It takes a pointer to a variable containing a simple time and converts it to the broken-down time format. But the result is not placed in a static buffer. Instead it is placed @@ -575,11 +640,9 @@ object the result was written into, i.e., it returns @var{resultp}. @comment ISO @deftypefun {struct tm *} gmtime (const time_t *@var{time}) This function is similar to @code{localtime}, except that the broken-down -time is expressed as Coordinated Universal Time (UTC)---that is, as -Greenwich Mean Time (GMT)---rather than relative to the local time zone. +time is expressed as Coordinated Universal Time (UTC) (formerly called +Greenwich Mean Time (GMT)) rather than relative to a local time zone. -Recall that calendar times are @emph{always} expressed in coordinated -universal time. @end deftypefun As for the @code{localtime} function we have the problem that the result @@ -601,19 +664,19 @@ object the result was written into, i.e., it returns @var{resultp}. @comment ISO @deftypefun time_t mktime (struct tm *@var{brokentime}) The @code{mktime} function is used to convert a broken-down time structure -to a calendar time representation. It also ``normalizes'' the contents of +to a simple time representation. It also ``normalizes'' the contents of the broken-down time structure, by filling in the day of week and day of year based on the other date and time components. The @code{mktime} function ignores the specified contents of the @code{tm_wday} and @code{tm_yday} members of the broken-down time -structure. It uses the values of the other components to compute the +structure. It uses the values of the other components to determine the calendar time; it's permissible for these components to have unnormalized values outside their normal ranges. The last thing that @code{mktime} does is adjust the components of the @var{brokentime} structure (including the @code{tm_wday} and @code{tm_yday}). -If the specified broken-down time cannot be represented as a calendar time, +If the specified broken-down time cannot be represented as a simple time, @code{mktime} returns a value of @code{(time_t)(-1)} and does not modify the contents of @var{brokentime}. @@ -621,6 +684,242 @@ Calling @code{mktime} also sets the variable @code{tzname} with information about the current time zone. @xref{Time Zone Functions}. @end deftypefun +@comment time.h +@comment ??? +@deftypefun time_t timelocal (struct tm *@var{brokentime}) + +@code{timelocal} is functionally identical to @code{mktime}, but more +mnemonically named. Note that it is the inverse of the @code{localtime} +function. + +@strong{Portability note:} @code{mktime} is essentially universally +available. @code{timelocal} is rather rare. + +@end deftypefun + +@comment time.h +@comment ??? +@deftypefun time_t timegm (struct tm *@var{brokentime}) + +@code{timegm} is functionally identical to @code{mktime} except it +always takes the input values to be Coordinated Universal Time (UTC) +regardless of any local time zone setting. + +Note that @code{timegm} is the inverse of @code{gmtime}. + +@strong{Portability note:} @code{mktime} is essentially universally +available. @code{timegm} is rather rare. For the most portable +conversion from a UTC broken-down time to a simple time, set +the @code{TZ} environment variable to UTC, call @code{mktime}, then set +@code{TZ} back. + +@end deftypefun + + + +@node High Accuracy Clock +@subsection High Accuracy Clock + +@cindex time, high precision +@cindex clock, high accuracy +@pindex sys/timex.h +@c On Linux, GNU libc implements ntp_gettime() and npt_adjtime() as calls +@c to adjtimex(). +The @code{ntp_gettime} and @code{ntp_adjtime} functions provide an +interface to monitor and manipulate the system clock to maintain high +accuracy time. For example, you can fine tune the speed of the clock +or synchronize it with another time source. + +A typical use of these functions is by a server implementing the Network +Time Protocol to synchronize the clocks of multiple systems and high +precision clocks. + +These functions are declared in @file{sys/timex.h}. + +@tindex struct ntptimeval +@deftp {Data Type} {struct ntptimeval} +This structure is used to monitor kernel time. It contains the +following members: +@table @code +@item struct timeval time +This is the current time. The @code{struct timeval} data type is +described in @ref{High-Resolution Calendar}. + +@item long int maxerror +This is the maximum error, measured in microseconds. Unless updated +via @code{ntp_adjtime} periodically, this value will reach some +platform-specific maximum value. + +@item long int esterror +This is the estimated error, measured in microseconds. This value can +be set by @code{ntp_adjtime} to indicate the estimated offset of the +local clock against the true time. +@end table +@end deftp + +@comment sys/timex.h +@comment GNU +@deftypefun int ntp_gettime (struct ntptimeval *@var{tptr}) +The @code{ntp_gettime} function sets the structure pointed to by +@var{tptr} to current values. The elements of the structure afterwards +contain the values the timer implementation in the kernel assumes. They +might or might not be correct. If they are not a @code{ntp_adjtime} +call is necessary. + +The return value is @code{0} on success and other values on failure. The +following @code{errno} error conditions are defined for this function: + +@table @code +@item TIME_ERROR +The precision clock model is not properly set up at the moment, thus the +clock must be considered unsynchronized, and the values should be +treated with care. +@end table +@end deftypefun + +@tindex struct timex +@deftp {Data Type} {struct timex} +This structure is used to control and monitor the system clock. It +contains the following members: +@table @code +@item unsigned int modes +This variable controls whether and which values are set. Several +symbolic constants have to be combined with @emph{binary or} to specify +the effective mode. These constants start with @code{MOD_}. + +@item long int offset +This value indicates the current offset of the local clock from the true +time. The value is given in microseconds. If bit @code{MOD_OFFSET} is +set in @code{modes}, the offset (and possibly other dependent values) can +be set. The offset's absolute value must not exceed @code{MAXPHASE}. + + +@item long int frequency +This value indicates the difference in frequency between the true time +and the local clock. The value is expressed as scaled PPM (parts per +million, 0.0001%). The scaling is @code{1 << SHIFT_USEC}. The value +can be set with bit @code{MOD_FREQUENCY}, but the absolute value must +not exceed @code{MAXFREQ}. + +@item long int maxerror +This is the maximum error, measured in microseconds. A new value can be +set using bit @code{MOD_MAXERROR}. Unless updated via +@code{ntp_adjtime} periodically, this value will increase steadily +and reach some platform-specific maximum value. + +@item long int esterror +This is the estimated error, measured in microseconds. This value can +be set using bit @code{MOD_ESTERROR}. + +@item int status +This variable reflects the various states of the clock machinery. There +are symbolic constants for the significant bits, starting with +@code{STA_}. Some of these flags can be updated using the +@code{MOD_STATUS} bit. + +@item long int constant +This value represents the bandwidth or stiffness of the PLL (phase +locked loop) implemented in the kernel. The value can be changed using +bit @code{MOD_TIMECONST}. + +@item long int precision +This value represents the accuracy or the maximum error when reading the +system clock. The value is expressed in microseconds. + +@item long int tolerance +This value represents the maximum frequency error of the system clock in +scaled PPM. This value is used to increase the @code{maxerror} every +second. + +@item struct timeval time +The current time. + +@item long int tick +The time between clock ticks in microseconds. A clock tick is a +periodic timer interrupt on which the system clock is based. + +@item long int ppsfreq +This is the first of a few optional variables that are present only if +the system clock can use a PPS (pulse per second) signal to discipline +the local clock. The value is expressed in scaled PPM and it denotes +the difference in frequency between the local clock and the PPS signal. + +@item long int jitter +This value expresses a median filtered average of the PPS signal's +dispersion in microseconds. + +@item int shift +This value is a binary exponent for the duration of the PPS calibration +interval, ranging from @code{PPS_SHIFT} to @code{PPS_SHIFTMAX}. + +@item long int stabil +This value represents the median filtered dispersion of the PPS +frequency in scaled PPM. + +@item long int jitcnt +This counter represents the number of pulses where the jitter exceeded +the allowed maximum @code{MAXTIME}. + +@item long int calcnt +This counter reflects the number of successful calibration intervals. + +@item long int errcnt +This counter represents the number of calibration errors (caused by +large offsets or jitter). + +@item long int stbcnt +This counter denotes the number of of calibrations where the stability +exceeded the threshold. +@end table +@end deftp + +@comment sys/timex.h +@comment GNU +@deftypefun int ntp_adjtime (struct timex *@var{tptr}) +The @code{ntp_adjtime} function sets the structure specified by +@var{tptr} to current values. + +In addition, @code{ntp_adjtime} updates some settings to match what you +pass to it in *@var{tptr}. Use the @code{modes} element of *@var{tptr} +to select what settings to update. You can set @code{offset}, +@code{freq}, @code{maxerror}, @code{esterror}, @code{status}, +@code{constant}, and @code{tick}. + +@code{modes} = zero means set nothing. + +Only the superuser can update settings. + +@c On Linux, ntp_adjtime() also does the adjtime() function if you set +@c modes = ADJ_OFFSET_SINGLESHOT (in fact, that is how GNU libc implements +@c adjtime()). But this should be considered an internal function because +@c it's so inconsistent with the rest of what ntp_adjtime() does and is +@c forced in an ugly way into the struct timex. So we don't document it +@c and instead document adjtime() as the way to achieve the function. + +The return value is @code{0} on success and other values on failure. The +following @code{errno} error conditions are defined for this function: + +@table @code +@item TIME_ERROR +The high accuracy clock model is not properly set up at the moment, thus the +clock must be considered unsynchronized, and the values should be +treated with care. Another reason could be that the specified new values +are not allowed. + +@item EPERM +The process specified a settings update, but is not superuser. + +@end table + +For more details see RFC1305 (Network Time Protocol, Version 3) and +related documents. + +@strong{Portability note:} Early versions of the GNU C library did not +have this function but did have the synonymous @code{adjtimex}. + +@end deftypefun + + @node Formatting Date and Time @subsection Formatting Date and Time @@ -669,7 +968,7 @@ return @code{NULL}. @comment ISO @deftypefun {char *} ctime (const time_t *@var{time}) The @code{ctime} function is similar to @code{asctime}, except that the -time value is specified as a @code{time_t} calendar time value rather +time value is specified as a @code{time_t} simple time value rather than in broken-down local time format. It is equivalent to @smallexample @@ -1816,8 +2115,8 @@ effect. @node Time Functions Example @subsection Time Functions Example -Here is an example program showing the use of some of the local time and -calendar time functions. +Here is an example program showing the use of some of the calendar time +functions. @smallexample @include strftim.c.texi @@ -1832,169 +2131,6 @@ The time is 01:02 PM. @end smallexample -@node Precision Time -@section Precision Time - -@cindex time, high precision -@pindex sys/timex.h -The @code{ntp_gettime} and @code{ntp_adjtime} functions provide an -interface to monitor and manipulate high precision time. These -functions are declared in @file{sys/timex.h}. - -@tindex struct ntptimeval -@deftp {Data Type} {struct ntptimeval} -This structure is used to monitor kernel time. It contains the -following members: -@table @code -@item struct timeval time -This is the current time. The @code{struct timeval} data type is -described in @ref{High-Resolution Calendar}. - -@item long int maxerror -This is the maximum error, measured in microseconds. Unless updated -via @code{ntp_adjtime} periodically, this value will reach some -platform-specific maximum value. - -@item long int esterror -This is the estimated error, measured in microseconds. This value can -be set by @code{ntp_adjtime} to indicate the estimated offset of the -local clock against the true time. -@end table -@end deftp - -@comment sys/timex,h -@comment GNU -@deftypefun int ntp_gettime (struct ntptimeval *@var{tptr}) -The @code{ntp_gettime} function sets the structure pointed to by -@var{tptr} to current values. The elements of the structure afterwards -contain the values the timer implementation in the kernel assumes. They -might or might not be correct. If they are not a @code{ntp_adjtime} -call is necessary. - -The return value is @code{0} on success and other values on failure. The -following @code{errno} error conditions are defined for this function: - -@table @code -@item TIME_ERROR -The precision clock model is not properly set up at the moment, thus the -clock must be considered unsynchronized, and the values should be -treated with care. -@end table -@end deftypefun - -@tindex struct timex -@deftp {Data Type} {struct timex} -This structure is used to control and monitor kernel time in a greater -level of detail. It contains the following members: -@table @code -@item unsigned int modes -This variable controls whether and which values are set. Several -symbolic constants have to be combined with @emph{binary or} to specify -the effective mode. These constants start with @code{MOD_}. - -@item long int offset -This value indicates the current offset of the local clock from the true -time. The value is given in microseconds. If bit @code{MOD_OFFSET} is -set in @code{modes}, the offset (and possibly other dependent values) can -be set. The offset's absolute value must not exceed @code{MAXPHASE}. - -@item long int frequency -This value indicates the difference in frequency between the true time -and the local clock. The value is expressed as scaled PPM (parts per -million, 0.0001%). The scaling is @code{1 << SHIFT_USEC}. The value -can be set with bit @code{MOD_FREQUENCY}, but the absolute value must -not exceed @code{MAXFREQ}. - -@item long int maxerror -This is the maximum error, measured in microseconds. A new value can be -set using bit @code{MOD_MAXERROR}. Unless updated via -@code{ntp_adjtime} periodically, this value will increase steadily -and reach some platform-specific maximum value. - -@item long int esterror -This is the estimated error, measured in microseconds. This value can -be set using bit @code{MOD_ESTERROR}. - -@item int status -This variable reflects the various states of the clock machinery. There -are symbolic constants for the significant bits, starting with -@code{STA_}. Some of these flags can be updated using the -@code{MOD_STATUS} bit. - -@item long int constant -This value represents the bandwidth or stiffness of the PLL (phase -locked loop) implemented in the kernel. The value can be changed using -bit @code{MOD_TIMECONST}. - -@item long int precision -This value represents the accuracy or the maximum error when reading the -system clock. The value is expressed in microseconds and can't be changed. - -@item long int tolerance -This value represents the maximum frequency error of the system clock in -scaled PPM. This value is used to increase the @code{maxerror} every -second. - -@item long int ppsfreq -This is the first of a few optional variables that are present only if -the system clock can use a PPS (pulse per second) signal to discipline -the local clock. The value is expressed in scaled PPM and it denotes -the difference in frequency between the local clock and the PPS signal. - -@item long int jitter -This value expresses a median filtered average of the PPS signal's -dispersion in microseconds. - -@item int int shift -This value is a binary exponent for the duration of the PPS calibration -interval, ranging from @code{PPS_SHIFT} to @code{PPS_SHIFTMAX}. - -@item long int stabil -This value represents the median filtered dispersion of the PPS -frequency in scaled PPM. - -@item long int jitcnt -This counter represents the number of pulses where the jitter exceeded -the allowed maximum @code{MAXTIME}. - -@item long int calcnt -This counter reflects the number of successful calibration intervals. - -@item long int errcnt -This counter represents the number of calibration errors (caused by -large offsets or jitter). - -@item long int stbcnt -This counter denotes the number of of calibrations where the stability -exceeded the threshold. -@end table -@end deftp - -@comment sys/timex.h -@comment GNU -@deftypefun int ntp_adjtime (struct timex *@var{tptr}) -The @code{ntp_adjtime} function sets the structure specified by -@var{tptr} to current values. In addition, values passed in @var{tptr} -can be used to replace existing settings. To do this the @code{modes} -element of the @code{struct timex} must be set appropriately. Setting -it to zero selects reading the current state. - -The return value is @code{0} on success and other values on failure. The -following @code{errno} error conditions are defined for this function: - -@table @code -@item TIME_ERROR -The precision clock model is not properly set up at the moment, thus the -clock must be considered unsynchronized, and the values should be -treated with care. Another reason could be that the specified new values -are not allowed. -@end table - -For more details see RFC1305 (Network Time Protocol, Version 3) and -related documents. -@end deftypefun - - @node Setting an Alarm @section Setting an Alarm @@ -2263,4 +2399,3 @@ be protected using cancellation handlers. The @code{nanosleep} function is declared in @file{time.h}. @end deftypefun - |