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HP OpenVMS Systems Documentation |
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HP C
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Writes a character string to the standard output ( stdout ) followed by a new-line character.
#include <stdio.h>int puts (const char *str);
str
A pointer to a character string.
The puts function does not copy the terminating null character to the output stream.
Nonnegative value Indicates success. EOF Indicates output errors.
Writes characters to a specified file.
#include <stdio.h>int putw (int integer, FILE *file_ptr);
integer
An object of type int or long .file_ptr
A file pointer.
The putw function writes four characters to the output file as an int . No conversion is performed.
integer Indicates success. EOF Indicates output errors.
Converts a wide character to its corresponding multibyte value, and writes the result to a specified file.
#include <wchar.h>wint_t putwc (wint_t wc, FILE *file_ptr);
wc
An object of type wint_t .file_ptr
A file pointer.
Since putwc might be implemented as a macro, a file pointer argument with side effects (for example putwc (wc, *f++) ) might be evaluated incorrectly. In such a case, use the fputwc function instead.See also fputwc .
x The character written to the file. Indicates success. WEOF Indicates an output error. The function sets errno . For a list of the errno values set by this function, see fputwc .
Writes a wide character to the standard output ( stdout ) and returns the character.
#include <wchar.h>wint_t putwchar (wint_t wc);
wc
An object of type wint_t .
The putwchar function is identical to fputwc (wc, stdout ).
x The character written to the file. Indicates success. WEOF Indicates an output error. The function sets errno . For a list of the errno values set by this function, see fputwc .
Writes into a given position within a file without changing the file pointer.
#include <unistd.h>ssize_t pwrite (int file_desc, const void *buffer, size_t nbytes, off_t offset);
file_desc
A file descriptor that refers to a file currently opened for writing or updating.buffer
The address of contiguous storage from which the output data is taken.nbytes
The maximum number of bytes involved in the write operation.offset
The offset for the desired position inside the file.
The pwrite function performs the same action as write , except that it writes into a given position in the file without changing the file pointer. The first three arguments to pwrite are the same as for write , with the addition of a fourth argument offset for the desired position inside the file.
n The number of bytes written. - 1 Upon failure, the file pointer remains unchanged and pwrite sets errno to one of the following values:
- EINVAL -- The offset argument is invalid. The value is negative.
- ESPIPE -- fildes is associated with a pipe or FIFO.
Returns the absolute value of an integer as an __int64 . llabs is a synonym for qabs .
#include <stdlib.h>__int64 qabs (__int64 j);
__int64 llabs (__int64 j);
j
A value of type __int64 .
Returns the quotient and the remainder after the division of its arguments. lldiv is a synonym for qdiv .
#include <stdlib.h>qdiv_t qdiv (__int64 numer, __int64 denom);
lldiv_t lldiv (__int64 numer, __int64 denom);
numer
A numerator of type __int64 .denom
A denominator of type __int64 .
The types qdiv_t and lldiv_t are defined in the <stdlib.h> header file as follows:
typedef struct { __int64 quot, rem; } qdiv_t, lldiv_t;
Sorts an array of objects in place. It implements the quick-sort algorithm.
#include <stdlib.h>Function Variants The qsort function has variants named _qsort32 and _qsort64 for use with 32-bit and 64-bit pointer sizes, respectively. See Section 1.10 for more information on using pointer-size-specific functions.void qsort (void *base, size_t nmemb, size_t size, int (*compar) (const void *, const void *));
base
A pointer to the first member of the array. The pointer should be of type pointer-to-element and cast to type pointer-to-character.nmemb
The number of objects in the array.size
The size of an object, in bytes.compar
A pointer to the comparison function.
Two arguments are passed to the comparison function pointed to by compar. The two arguments point to the objects being compared. Depending on whether the first argument is less than, equal to, or greater than the second argument, the comparison function returns an integer less then, equal to, or greater than 0.The comparison function compar need not compare every byte, so arbitrary data might be contained in the objects in addition to the values being compared.
The order in the output of two objects that compare as equal is unpredictable.
Generates a specified software signal. Generating a signal causes the action routine established by the signal , ssignal , or sigvec function to be invoked.
#include <signal.h>int raise (int sig); (ANSI C)
int raise (int sig[, int sigcode]); (HP C EXTENSION)
sig
The signal to be generated.sigcode
An optional signal code, available only when not compiling in strict ANSI C mode. For example, signal SIGFPE---the arithmetic trap signal---has 10 different codes, each representing a different type of arithmetic trap.The signal codes can be represented by mnemonics or numbers. The arithmetic trap codes are represented by the numbers 1 to 10; the SIGILL codes are represented by the numbers 0 to 2. The code values are defined in the <signal.h> header file. See Tables 4-4 and 4-5 for a list of signal mnemonics, codes, and corresponding OpenVMS exceptions.
Calling the raise function has one of the following results:
- If raise specifies a sig argument that is outside the range defined in the <signal.h> header file, then the raise function returns 0, and the errno variable is set to EINVAL.
- If signal , ssignal , or sigvec establishes SIG_DFL (default action) for the signal, then the functions do not return. The image is exited with the OpenVMS error code corresponding to the signal.
- If signal , ssignal , or sigvec establishes SIG_IGN (ignore signal) as the action for the signal, then raise returns its argument, sig.
- signal , ssignal , or sigvec must establish an action function for the signal. That function is called and its return value is returned by raise .
See Chapter 4 for more information on signal processing.
See also gsignal , signal , ssignal , and sigvec .
0 If successful. nonzero If unsuccessful.
Returns pseudorandom numbers in the range 0 to 231 - 1.
#include <math.h>int rand (void);
int rand_r (unsigned int seed); (ALPHA ONLY)
seed
An initial seed value.
The rand function computes a sequence of pseudorandom integers in the range 0 to {RAND_MAX} with a period of at least 232.The rand_r function computes a sequence of pseudorandom integers in the range 0 to {RAND_MAX}. The value of the {RAND_MAX} macro will be at least 32767.
If rand_r is called with the same initial value for the object pointed to by seed and that object is not modified between successive returns and calls to rand_r , the same sequence is generated.
See also srand .
For other random-number algorithms, see random and all the * 48 functions.
n A pseudorandom number.
Generates pseudorandom numbers in a more random sequence.
#include <stdlib.h>long int random (void);
The random function is a random-number generator that has virtually the same calling sequence and initialization properties as the rand function, but produces sequences that are more random. The low 12 bits generated by rand go through a cyclic pattern. All bits generated by random are usable. For example, random () &1 produces a random binary value.The random function uses a nonlinear, additive-feedback, random-number generator employing a default state-array size of 31 integers to return successive pseudorandom numbers in the range from 0 to 231-1 . The period of this random-number generator is approximately 16*( 231-1 ). The size of the state array determines the period of the random-number generator. Increasing the state array size increases the period.
With a full 256 bytes of state information, the period of the random-number generator is greater than 269 , and is sufficient for most purposes.
Like the rand function, the random function produces by default a sequence of numbers that you can duplicate by calling the srandom function with a value of 1 as the seed. The srandom function, unlike the srand function, does not return the old seed because the amount of state information used is more than a single word.
See also rand , srand , srandom , setstate , and initstate .
n A random number.
Raw mode only works with the Curses input routines [w]getch and [w]getstr . Raw mode is not supported with the HP C RTL emulation of UNIX I/O, Terminal I/O, or Standard I/O.
#include <curses.h>raw()
noraw()
Raw mode reads are satisfied on one of two conditions: after a minimum number (5) of characters are input at the terminal or after waiting a fixed time (10 seconds) from receipt of any characters from the terminal.
/* Example of standard and raw input in Curses package. */ #include <curses.h> main() { WINDOW *win1; char vert = '.', hor = '.', str[80]; /* Initialize standard screen, turn echo off. */ initscr(); noecho(); /* Define a user window. */ win1 = newwin(22, 78, 1, 1); leaveok(win1, TRUE); leaveok(stdscr, TRUE); box(stdscr, vert, hor); /* Reset the video, refresh(redraw) both windows. */ mvwaddstr(win1, 2, 2, "Test line terminated input"); wrefresh(win1); /* Do some input and output it. */ nocrmode(); wgetstr(win1, str); mvwaddstr(win1, 5, 5, str); mvwaddstr(win1, 7, 7, "Type something to clear screen"); wrefresh(win1); /* Get another character then delete the window. */ wgetch(win1); wclear(win1); mvwaddstr(win1, 2, 2, "Test raw input"); wrefresh(win1); /* Do some raw input 5 chars or timeout - and output it. */ raw(); getstr(str); noraw(); mvwaddstr(win1, 5, 5, str); mvwaddstr(win1, 7, 7, "Raw input completed"); wrefresh(win1); endwin(); }
Reads bytes from a file and places them in a buffer.
#include <unistd.h>ssize_t read (int file_desc, void *buffer, size_t nbytes); (ISO POSIX-1)
int read (int file_desc, void *buffer, int nbytes); (COMPATABILITY)
file_desc
A file descriptor. The specified file descriptor must refer to a file currently opened for reading.buffer
The address of contiguous storage in which the input data is placed.nbytes
The maximum number of bytes involved in the read operation.
The read function returns the number of bytes read. The return value does not necessarily equal nbytes. For example, if the input is from a terminal, at most one line of characters is read.
Note
The read function does not span record boundaries in a record file and, therefore, reads at most one record. A separate read must be done for each record.
n The number of bytes read. - 1 Indicates a read error, including physical input errors, illegal buffer addresses, protection violations, undefined file descriptors, and so forth.
#include <file.h> #include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <fcntl.h> main() { int fd, i; char buf[10]; FILE *fp ; /* Temporary STDIO file */ /* Create a dummy data file */ if ((fp = fopen("test.txt", "w+")) == NULL) { perror("open"); exit(1); } fputs("XYZ\n",fp) ; fclose(fp) ; /* And now practice "read" */ if ((fd = open("test.txt", O_RDWR, 0, "shr=upd")) <= 0) { perror("open"); exit(0); } /* Read 2 characters into buf. */ if ((i = read(fd, buf, 2)) < 0) { perror("read"); exit(0); } /* Print out what was read. */ if (i > 0) printf("buf='%c%c'\n", buf[0], buf[1]); close(fd); }
Finds entries in a directory.
#include <dirent.h>struct dirent *readdir (DIR *dir_pointer);
int readdir_r (DIR *dir_pointer, struct dirent *entry, struct dirent **result);
dir_pointer
A pointer to the dir structure of an open directory.entry
A pointer to a dirent structure that will be initialized with the directory entry at the current position of the specified stream.result
Upon successful completion, the location where a pointer to entry is stored.
The readdir function returns a pointer to a structure representing the directory entry at the current position in the directory stream specified by dir_pointer, and positions the directory stream at the next entry. It returns a NULL pointer upon reaching the end of the directory stream. The dirent structure defined in the <dirent.h> header file describes a directory entry.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.
The pointer returned by the readdir function points to data that you can overwrite by another call to readdir on the same directory stream. This data is not overwritten by another call to readdir on a different directory stream.
If a file is removed from or added to the directory after the most recent call to the opendir or rewinddir function, a subsequent call to the readdir function might not return an entry for that file.
When it reaches the end of the directory, or when it detects an invalid seekdir operation, the readdir function returns the null value.
An attempt to seek to an invalid location causes the readdir function to return the null value the next time it is called. A previous telldir function call returns the position.
The readdir_r function is a reentrant version of readdir . In addition to dir_pointer, you must specify a pointer to a dirent structure in which the current directory entry of the specified stream is returned.
If the operation is successful, readdir_r returns 0 and stores one of the two following pointers in result:
- Pointer to entry if the entry was found
- NULL pointer if the end of the directory stream was reached
If an error occurred, an error value is returned that indicates the cause of the error.
The storage pointed to by entry must be large enough for a dirent with an array of char d_name member containing at least NAME_MAX + 1 elements.
See the description of closedir for an example.
x On successful completion of readdir , a pointer to an object of type struct dirent . 0 Successful completion of readdir_r . x On error, an error value ( readdir_r only). NULL An error occurred or end of the directory stream ( readdir_r only). If an error occurred, errno is set to a value indicating the cause.
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