HP OpenVMS Systems

Resets the position of the specified directory stream to the beginning of a directory.

Format

#include <dirent.h>

void rewinddir (DIR *dir_pointer);

Argument

dir_pointer

A pointer to the dir structure of an open directory.

Description

The rewinddir function resets the position of the specified directory stream to the beginning of the directory. It also causes the directory stream to refer to the current state of the corresonding directory, the same as using the opendir function. If the dir_pointer argument does not refer to a directory stream, the effect is undefined.

The type DIR , defined in the <dirent.h> header file, represents a directory stream. A directory stream is an ordered sequence of all the directory entries in a particular directory. Directory entries represent files.

See also opendir .

Searches for a character in a string.

Format

#include <strings.h>

char *rindex (const char *s, int c);

Arguments

s

The string to search.

c

The character to search for.

Description

The rindex function is identical to the strchr function, and is provided for compatibility with some UNIX implementations.

Rounds its argument to an integral value according to the current IEEE rounding direction specified by the user.

Format

#include <math.h>

double rint (double x);

float rintf (float x,);

long double rintl (long double x);

Argument

x

A real number.

Description

The rint functions return the nearest integral value to x in the direction of the current IEEE rounding mode specified on the /ROUNDING_MODE command-line qualifier.

If the current rounding mode rounds toward negative Infinity, then rint is identical to floor . If the current rounding mode rounds toward positive Infinity, then rint is identical to ceil .

If |x| = Infinity, rint returns x.

Return Values

n	The nearest integral value to x in the direction of the current IEEE rounding mode.
NaN	x is NaN; errno is set to EDOM.

Removes a directory file.

Format

#include <unistd.h>

int rmdir (const char *path);

Argument

path

A directory pathname.

Description

The rmdir function removes a directory file whose name is specified in the path argument. The directory is removed only if it is empty.

Restriction

When using OpenVMS format names, the path argument must be in the form directory.dir.

Return Values

0	Indicates success.
- 1	An error occurred; errno is set to indicate the error.

Determines the lowest virtual address that is not used with the program.

Format

#include <unistd.h>

void *sbrk (long int incr);

Argument

incr

The number of bytes to add to the current break address.

Description

The sbrk function adds the number of bytes specified by its argument to the current break address and returns the old break address.

When a program is executed, the break address is set to the highest location defined by the program and data storage areas. Consequently, sbrk is needed only by programs that have growing data areas.

sbrk(0) returns the current break address.

Return Values

x	The old break address.
( void *)( - 1)	Indicates that the program is requesting too much memory.

Restriction

Unlike other C library implementations, the HP C RTL memory allocation functions (such as malloc ) do not rely on brk or sbrk to manage the program heap space. Consequently, on OpenVMS systems, calling brk or sbrk can interfere with memory allocation routines. The brk and sbrk functions are provided only for compatibility purposes.

Returns the exponent of a floating-point number.

Format

#include <math.h>

double scalb (double x, double n);

float scalbf (float x, float n);

long double scalbl (long double x, long double n);

Arguments

x

A nonzero floating-point number.

n

An integer.

Description

The scalb functions return x*(2**n) for integer n.

Return Values

x	On successful completion, x*(2** n) is returned.
±HUGE_VAL	On overflow, scalb returns ±HUGE_VAL (according to the sign of x) and sets errno to ERANGE.
0	Underflow occurred; errno is set to ERANGE.
x	x is ±Infinity.
NaN	x or n is NaN; errno is set to EDOM.

Performs formatted input from the standard input ( stdin ), interpreting it according to the format specification. See Chapter 2 for information on format specifiers.

Format

#include <stdio.h>

int scanf (const char *format_spec, ...);

Arguments

format_spec

Pointer to a string containing the format specification. The format specification consists of characters to be taken literally from the input or converted and placed in memory at the specified input sources. For a list of conversion characters, see Chapter 2.

...

Optional expressions that are pointers to objects whose resultant types correspond to conversion specifications given in the format specification.

If no conversion specifications are given, you can omit these input pointers. Otherwise, the function call must have at least as many input pointers as there are conversion specifications, and the conversion specifications must match the types of the input pointers.

Conversion specifications are matched to input sources in left-to-right order. Excess input pointers, if any, are ignored.

Return Values

x	The number of successfully matched and assigned input items.
EOF	Indicates that a read error occurred prior to any successful conversions.The function sets errno . For a list of errno values set by this function, see fscanf .

Perform a scanf on the window. The scanw function acts on the stdscr window.

Format

#include <curses.h>

int scanw (char *format_spec, ...);

int wscanw (WINDOW *win, char *format_spec, ...);

Arguments

win

A pointer to the window.

format_spec

A pointer to the format specification string.

...

Optional expressions that are pointers to objects whose resultant types correspond to conversion specifications given in the format specification. If no conversion specifications are given, you may omit these input pointers.

Otherwise, the function call must have at least as many input pointers as there are conversion specifications, and the conversion specifications must match the types of the input pointers.

Conversion specifications are matched to input sources in left-to-right order. Excess input pointers, if any, are ignored.

Description

The formatting specification (format_spec) and the other arguments are identical to those used with the scanf function.

The scanw and wscanw functions accept, format, and return a line of text from the terminal screen. For more information, see the scrollok and scanf functions.

Return Values

OK	Indicates success.
ERR	Indicates that the function makes the screen scroll illegally or that the scan was unsuccessful.

Moves all the lines on the window up one line. The top line scrolls off the window and the bottom line becomes blank.

Format

#include <curses.h>

int scroll (WINDOW *win);

Argument

win

A pointer to the window.

Return Values

OK	Indicates success.
ERR	Indicates an error.

Sets the scroll flag for the specified window.

Format

#include <curses.h>

scrollok (WINDOW *win, bool boolf);

Arguments

win

A pointer to the window.

boolf

A Boolean TRUE or FALSE value. If boolf is FALSE, scrolling is not allowed. This is the default setting. The bool type is defined in the <curses.h> header file as follows:

#define bool int

Initializes a 48-bit random-number generator.

Format

#include <stdlib.h>

unsigned short *seed48 (unsigned short seed_16v[3]);

Argument

seed_16v

An array of three unsigned short int s that form a 48-bit seed value.

Description

The seed48 function initializes the random-number generator. You can use this function in your program before calling the drand48 , lrand48 , or mrand48 functions. (Although it is not recommended practice, constant default initializer values are supplied automatically if you call drand48 , lrand48 , or mrand48 without calling an initialization function).

The seed48 function works by generating a sequence of 48-bit integer values, Xi, according to the linear congruential formula:

Xn+1 = (aXn+c)mod m n > 0

The argument m equals 2⁴⁸ , so 48-bit integer arithmetic is performed. Unless you invoke the lcong48 function, the multiplier value a and the addend value c are:

a = 5DEECE66D16 = 2736731631558 c = B16 = 138

The initializer function seed48 :

• Sets the value of Xi to the 48-bit value specified in the array pointed to by seed_16v.
• Returns a pointer to a 48-bit internal buffer that contains the previous value of Xi, used only by seed48 .

The returned pointer allows you to restart the pseudorandom sequence at a given point. Use the pointer to copy the previous Xi value into a temporary array. To resume where the original sequence left off, you can call seed48 with a pointer to this array.

See also drand48 , lrand48 , and mrand48 .

Return Value

x	A pointer to a 48-bit internal buffer.

Sets the position of a directory stream.

Format

#include <dirent.h>

void seekdir (DIR *dir_pointer, long int location);

Arguments

dir_pointer

A pointer to the dir structure of an open directory.

location

The number of an entry relative to the start of the directory.

Description

The seekdir function sets the position of the next readdir operation on the directory stream specified by dir_pointer to the position specified by location. The value of location should be returned from an earlier call to telldir.

If the value of location was not returned by a call to the telldir function, or if there was an intervening call to the rewinddir function on this directory stream, the effect is unspecified.

The type DIR , defined in the <dirent.h> header file, represents a directory stream. A directory stream is an ordered sequence of all the directory entries in a particular directory. Directory entries represent files. You can remove files from or add files to a directory asynchronously to the operation of the readdir function.

See readdir , rewinddir , and telldir .

Activate the video display attribute attr within the window. The setattr function acts on the stdscr window.

Format

#include <curses.h>

int setattr (int attr);

int wsetattr (WINDOW *win, int attr);

Arguments

win

A pointer to the window.

attr

One of a set of video display attributes, which are blinking, boldface, reverse video, and underlining, and are represented by the defined constants _BLINK, _BOLD, _REVERSE, and _UNDERLINE, respectively. You can set multiple attributes by separating them with a bitwise OR operator (|) as follows:

setattr(_BLINK | _UNDERLINE);

Description

The setattr and wsetattr functions are specific to HP C for OpenVMS Systems and are not portable.

Return Values

OK	Indicates success.
ERR	Indicates an error.

Associates a new buffer with an input or output file and potentially modifies the buffering behavior.

Format

#include <stdio.h>

void setbuf (FILE *file_ptr, char *buffer);

Arguments

file_ptr

A file pointer.

buffer

A pointer to a character array or a NULL pointer.

Description

You can use the setbuf function after the specified file is opened but before any I/O operations are performed.

If buffer is a NULL pointer, then the call is equivalent to a call to setvbuf with the same file_ptr, a NULL buffer pointer, a buffering type of _IONBF (no buffering), and a buffer size of 0.

If buffer is not a NULL pointer, then the call is equivalent to a call to setvbuf with the same file_ptr, the same buffer pointer, a buffering type of _IOFBF, and a buffer size given by the value BUFSIZ (defined in <stdio.h> ). Therefore, use BUFSIZ to allocate the buffer argument used in the call to setbuf . For example:

#include <stdio.h> . . . char my_buf[BUFSIZ]; . . . setbuf(stdout, my_buf); . . .

User programs must not depend on the contents of buffer once I/O has been performed on the stream. The HP C RTL might or might not use buffer for any given I/O operation.

The setbuf function originally allowed programmers to substitute larger buffers in place of the system default buffers in obsolete versions of UNIX. The large default buffer sizes in modern implementations of C make the use of this function unnecessary most of the time. The setbuf function is retained in the ANSI C standard for compatibility with old programs. New programs should use setvbuf instead, because it allows the programmer to bind the buffer size at run time instead of compile time, and it returns a result value that can be tested.

Inserts or resets the environment variable specified by name in the current environment list.

Format

#include <stdlib.h>

int setenv (const char *name, const char *value, int overwrite);

Arguments

name

A variable name in the environment variable list.

value

The value for the environment variable.

overwrite

A value of 0 or 1 indicating whether to reset the environment variable, if it exists.

Description

The setenv function inserts or resets the environment variable name in the current environment list. If the variable name does not exist in the list, it is inserted with the value argument. If the variable does exist, the overwrite argument is tested. When the overwrite argument value is:

• 0 then the variable is not reset.
• 1 then the variable is reset to value.

Note Do not use the setenv , getenv , and putenv functions to manipulate symbols and logicals. Instead, use the OpenVMS library calls lib$set_logical , lib$get_logical , lib$set_symbol , and lib$get_symbol . The * env functions deliberately provide UNIX behavior, and are not a substitute for these OpenVMS runtime library calls. OpenVMS DCL symbols, not logical names, are the closest analog to environment variables on UNIX systems. While getenv is a mechanism to retrieve either a logical name or a symbol, it maintains an internal cache of values for use with setenv and subsequent getenv calls. The setenv function does not write or create DCL symbols or OpenVMS logical names. This is consistent with UNIX behavior. On UNIX systems, setenv does not change or create any symbols that will be visible in the shell after the program exits.

Return Values

0	Indicates success.
- 1	Indicates an error. errno is set to ENOMEM---Not enough memory available to expand the environment list.