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Returns a pointer to the null-terminated name of the terminal device associated with file descriptor 0, the default input device (stdin).
#include <unixio.h>char *ttyname (void);
This function is provided only for UNIX compatibility and has limited use in the OpenVMS environment.
x A pointer to a null-terminated string. 0 Indicates that SYS$INPUT is not a TTY device.
Sets and accesses time-zone conversion.
#include <time.h>void tzset (void);
extern char *tzname[];
extern long int timezone;
extern int daylight;
This function initializes time conversion information used by the ctime , localtime , mktime , strftime , and wcsftime functions.
The tzset function sets the following external variables:
- tzname is set as follows, where "std" is a 3-byte name for the standard time zone, and "dst" is a 3-byte name for the Daylight Savings Time zone:
tzname[0] = "std" tzname[1] = "dst"- daylight is set to 0 if Daylight Savings Time should never be applied to the time zone. Otherwise, daylight is set to 1.
- timezone is set to the difference between UTC and local standard time.
The environment variable tz specifies how tzset initializes time conversion information:
- If tz is absent from the environment, the implementation-dependent time-zone information is used, as follows:
The best available approximation to local wall-clock time is used, as defined by the system logical SYS$LOCALTIME, which points to a tzfile format file that describes default time-zone rules.
This system logical is set during the installation of OpenVMS Version 7.0 or higher to define a time-zone file based off the root directory SYS$COMMON:[SYS$ZONEINFO.SYSTEM]. 1- If tz appears in the environment but its value is a null string, Coordinated Universal Time (UTC) is used (without leap-second correction).
- If tz appears in the environment and its value is not a null string, the value has one of three formats, as described in Table REF-11.
Table REF-11 Time-Zone Initialization Rules tz Format Meaning : UTC is used. : pathname The characters following the colon specify the pathname of a tzfile format file from which to read the time-conversion information. A pathname beginning with a slash (/) represents an absolute pathname; otherwise, the pathname is relative to the system time-conversion information directory specified by SYS$TZDIR, which by default is SYS$COMMON:[SYS$ZONEINFO.SYSTEM]. stdoffset[ dst[ offset]
[,rule]]The value is first used as the pathname of a file (as described for the : pathname format) from which to read the time-conversion information. If that file cannot be read, the value is then interpreted as a direct specification of the time-conversion information, as follows:
std and dst---Three or more characters that are the designation for the time zone:
- std---Standard time zone. Required.
- dst---Daylight Savings Time zone. Optional. If dst is omitted, Daylight Savings Time does not apply.
Uppercase and lowercase letters are explicitly allowed. Any characters are allowed, except the following:
- digits
- leading colon (:)
- comma (,)
- minus (-)
- plus (+)
- ASCII null character
offset---The value added to the local time to arrive at UTC. The offset has the following format: hh[: mm[: ss]]
In this format:
- hh (hours) is a one-or two-digit value of 0--24.
- mm (minutes) is a value of 0--59. (optional)
- ss (seconds) is a value of 0--59. (optional)
The offset following std is required. If no offset follows dst, summer time is assumed, one hour ahead of standard time. You can use one or more digits; the value is always interpreted as a decimal number. If the time zone is preceded by a minus sign (-), the time zone is East of Greenwich; otherwise, it is West, which can also be indicated by a preceding plus sign (+).
rule---Indicates when to change to and return from summer time. The rule has the form: start[/ time], end[/ time]
Where:
- start is the date when the change from standard time to summer time occurs.
- end is the date for returning from summer time to standard time.
If start and end are omitted, the default is the US Daylight Saving Time start and end dates. The format for start and end must be one of the following:
- Jn---The Julian day n (1 < n < 365). Leap days are not counted. That is, in all years, including leap years, February 28 is day 59 and March 1 is day 60. You cannot explicitly refer to February 29.
- n---The zero based Julian day (0 < n < 365). Leap days are counted, making it possible to refer to February 29.
- Mm.n.d---The nth d day of month m where:
0 < n < 5, 0 < d < 6, 1 < m < 12.
When n is 5, it refers to the last d day of month m. Sunday is day 0.
time---The time when, in current time, the change to or return from summer time occurs. The time argument has the same format as offset, except that you cannot use a leading minus (-) or plus (+) sign. If time is not specified, the default is 02:00:00. If no rule is present in the tz specification, the rules used are those specified by the tzfile format file defined by the system logical SYS$POSIXRULES in the system time-conversion information directory, with the standard and summer time offsets from UTC replaced by those specified by the offset values in tz .
If tz does not specify a tzfile format file and cannot be interpreted as a direct specification, UTC is used.
See also ctime , localtime , mktime , strftime , and wcsftime in this section.
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EST5EDT4,M4.1.0,M10.5.0
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This sample TZ specification describes the rule defined in 1987 for the Eastern time zone in the US:
- EST (Eastern Standard Time) is the designation for standard time, which is 5 hours behind UTC.
- EDT (Eastern Daylight Time) is the designation for summer time, which is 4 hours behind UTC. EDT starts on the first Sunday in April and ends on the last Sunday in October.
Because time was not specified in either case, the changes occur at the default time, which is 2:00 a.m. The start and end dates did not need to be specified, because they are the defaults.
1 The Compaq C RTL uses a public-domain, time-zone handling package that puts time-zone conversion rules in easily accessible and modifiable files. These files reside in the directory SYS$COMMON:[SYS$ZONEINFO.SYSTEM.SOURCES]. zic converts these files to a special format described by the <tzfile.h> header file. The converted files are created with a root directory of SYS$COMMON:[SYS$ZONEINFO.SYSTEM], which is pointed to by the SYS$TZDIR system logical. This format is readable by the C library functions that handle time-zone information. For example, in the eastern United Stated, SYS$LOCALTIME is defined to be SYS$COMMON:[SYS$ZONEINFO.SYSTEM.US]EASTERN. |
Sets or changes the timeout of interval timers.
#include <unistd.h>useconds_t ualarm (useconds_t mseconds, useconds_t interval);
mseconds
Specifies a number of real time microseconds.interval
Specifies the interval for repeating the timer.
This function causes the sigalrm signal to be generated for the calling process after the number of real-time microseconds specified by useconds has elapsed. When the interval argument is nonzero, repeated timeout notification occurs with a period in microseconds specified by interval. If the notification signal sigalrm is not caught or is ignored, the calling process is terminated.If you call a combination of ualarm and setitimer functions, and the AST status is disabled, the return value is invalid.
If you call a combination of ualarm and setitimer functions, and the AST status is enabled, the return value is valid.
This is because you cannot invoke an AST handler to clear the previous value of the timer when ASTs are disabled or invoked from a handler that was invoked at AST level.
Note
Interactions between ualarm and either alarm , or sleep are unspecified.See also setitimer in this section.
n The number of microseconds remaining from the previous ualarm or setitimer call. 0 No timeouts are pending or ualarm not previously called. --1 Indicates an error.
Creates a file protection mask that is used when a new file is created, and returns the previous mask value.
#include <stat.h>mode_t umask (mode_t mode_complement);
mode_complement
Shows which bits to turn off when a new file is created. See the description of chmod to determine what the bits represent.
Initially, the file protection mask is set from the current process's default file protection. This is done when the C main program starts up or when decc$crtl_init (or vaxc$crtl_init ) is called. You can change this for all files created by your program by calling umask or you can use chmod to change the file protection on individual files. The file protection of a file created by open or creat is the bitwise AND of the open and creat mode argument with the complement of the value passed to umask on the previous call.
Note
The way to create files with OpenVMS RMS default protections using the UNIX system-call functions umask , mkdir , creat , and open is to call mkdir , creat , and open with a file-protection mode argument of 0777 in a program that never specifically calls umask . These default protections include correctly establishing protections based on ACLs, previous versions of files, and so on.
In programs that do vfork / exec calls, the new process image inherits whether umask has ever been called or not from the calling process image. The umask setting and whether the umask function has ever been called are both inherited attributes.
x The old mask value.
Gets system identification information.
#include <utsname.h>int uname (struct utsname *name);
name
The current system identifier.
This function stores null-terminated strings of information identifying the current system into the structure referenced by the name argument.The utsname structure is defined in the <utsname.h> header file and contains the following members:
sysname Name of the operating system implementation nodename Network name of this machine release Release level of the operating system version Version level of the operating system machine Machine hardware platform
0 Indicates success. --1 Indicates an error; errno or vaxc$errno is set as appropriate.
Pushes a character back into the input stream and leaves the stream positioned before the character.
#include <stdio.h>int ungetc (int character, FILE *file_ptr);
character
A value of type int .file_ptr
A file pointer.
When using this function, the character is pushed back onto the file indicated by file_ptr.One pushback is guaranteed, even if there has been no previous activity on the file. The fseek function erases all memory of pushed-back characters. The pushed-back character is not written to the underlying file. If the character to be pushed back is EOF, the operation fails, the input stream is left unchanged, and EOF is returned.
See also fseek and getc in this section.
x The push-back character. EOF Indicates it cannot push the character back.
Pushes a wide character back into the input stream.
#include <wchar.h>wint_t ungetwc (wint_t wc, FILE *file_ptr);
wc
A value of type wint_t .file_ptr
A file pointer.
When using this function, the wide character is pushed back onto the file indicated by file_ptr.One push-back is guaranteed, even if there has been no previous activity on the file. If a file positioning function (such as fseek ) is called before the pushed back character is read, the bytes representing the pushed back character are lost.
If the character to be pushed back is WEOF, the operation fails, the input stream is left unchanged, and WEOF is returned.
See also getwc in this section.
x The push-back character. WEOF Indicates that the function cannot push the character back. errno is set to one of the following:
- EBADF -- The file descriptor is not valid.
- EALREADY -- Operation is already in progress on the same file.
- EILSEQ -- Invalid wide-character code detected.
Deletes all instances of the environment variable name from the environment list.
#include <stdlib.h>void unsetenv (const char *name);
name
The environment variable to delete from the environment list.
This function deletes all instances of the variable name pointed to by the name argument from the environment list.
Suspends execution for an interval.
#include <unistd.h>int usleep (unsigned int mseconds);
mseconds
The number of microseconds to suspend execution for.
This function suspends the current process from execution for the number of microseconds specified by the mseconds argument. This argument must be less than 1,000,000. However, if its value is 0, then the call has no effect.There is one real-time interval timer for each process. The usleep function does not interfere with a previous setting of this timer. If the process set this timer before calling usleep and if the time specified by mseconds equals or exceeds the interval timer's prior setting, then the process is awakened shortly before the timer was set to expire.
0 Indicates success. --1 Indicates an error occurred; errno is set to EINVAL.
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