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Passes the name of an image to be activated in a child process. This function is nonreentrant.
#include <unistd.h>int execvp (const char *file_name, char *argv[]);
file_name
The file name of a new image to be activated in the child process. The device and directory specification for the file is obtained by searching the environment name VAXC$PATH.argv
An array of pointers to null-terminated character strings. These strings constitute the argument list available to the new process. By convention, argv[0] must point to a string that is the same as the new process file name (or its last component). argv is terminated by a NULL pointer.
See execl in this section for a description of how the exec functions operate.
--1 Indicates failure.
Terminate execution of the program from which they are called. These functions are nonreentrant.
#include <stdlib.h>void exit (int status);
#include <unistd.h>
void _exit (int status);
status
A status value of EXIT_SUCCESS (0), EXIT_FAILURE (1), or a number from 2 to 255:
- A status value of 0 or EXIT_SUCCESS is translated to the OpenVMS SS$_NORMAL status code to return the OpenVMS success value.
- A status value of 1 or EXIT_FAILURE is translated to an error-level exit status. The status value is passed to the parent process.
- Any other status value is left the same.
To use these status values as described, include <unistd.h> and compile with the _posix_exit feature-test macro set (either with /DEFINE=_POSIX_EXIT or with #define _posix_exit at the top of your file, before any file inclusions). This behavior is available only on OpenVMS Version 7.0 and higher systems.
If the process was invoked by the DIGITAL Command Language (DCL), the status is interpreted by DCL and a message is displayed.If the process was a child process created using vfork or an exec function, then the child process exits and control returns to the parent. The two functions are identical; the _exit function is retained for reasons of compatibility with VAX C.
The exit and _exit functions make use of the $EXIT system service. If your process is being invoked by the RUN command using any of the hibernation and scheduled wakeup qualifiers, the process might not correctly return to hibernation state when an exit or _exit call is made.
Note
EXIT_SUCCESS and EXIT_FAILURE are portable across any ANSI C compiler to indicate success or failure. On OpenVMS systems, they are mapped to OpenVMS condition codes with the severity set to success or failure, respectively. Values in the range of 2 to 255 can be used by a child process to communicate a small amount of data to the parent. The parent retreives this data using the wait , wait3 , wait4 , or waitpid functions.
Returns the base e raised to the power of the argument.
#include <math.h>double exp (double x);
x
A real value.
If an overflow occurs, the exp function returns the largest possible floating-point value and sets errno to ERANGE. The constant HUGE_VAL is defined in the <math.h> header file to be the largest possible floating-point value.
x The base e raised to the power of the argument. HUGE_VAL Indicates overflow; errno is set to ERANGE.
Returns the absolute value of a floating-point value.
#include <math.h>double fabs (double x);
x
A real value.
x The absolute value of the argument.
Closes a file by flushing any buffers associated with the file control block and freeing the file control block and buffers previously associated with the file pointer.
#include <stdio.h>int fclose (FILE *file_ptr);
file_ptr
A pointer to the file to be closed.
When a program terminates normally, the fclose function is automatically called for all open files.The fclose function tries to write buffered data by using an implicit call to fflush .
If the write fails (because the disk is full or the user's quota is exceeded, for example), fclose continues executing. It closes the VMS channel, deallocates any buffers, and releases the memory associated with the file descriptor (or FILE pointer). Any buffered data is lost, and the file descriptor (or FILE pointer) no longer refers to the file.
If your program needs to recover from errors when flushing buffered data, it should make an explicit call to fsync (or fflush ) before calling fclose .
0 Indicates success. EOF Indicates that the file control block is not associated with an open file.
Performs controlling operations on an open file.
#include <sys/types.h>#include <unistd.h>
#include <fcntl.h>
int fcntl (int file_desc, int request [, int file_desc2]);
file_desc
An open file descriptor obtained from a successful open , fcntl , or pipe function.request
The operation to be performed.file_desc2
A variable that depends on the value of the request parameter.
The fcntl function performs controlling operations on the open file specified by the file_desc parameter.The values for the request parameter are defined in the header file <fcntl.h> , and include the following:
F_DUPFD Returns a new file descriptor that is the lowest numbered available (that is, not already open) file descriptor greater than or equal to the third argument ( file_desc2) taken as an integer of type int . The new file descriptor refers to the same file as the original file descriptor ( file_desc). The FD_CLOEXEC flag associated with the new file descriptor is cleared to keep the file open across calls to one of the exec functions.
The following two calls are equivalent:
fid = dup(file_desc);
fid = fcntl(file_desc, F_DUPFD, 0);
The following call
fid = dup2(file_desc, file_desc2);
is similar (but not equivalent) to:
close(file_desc2);
fid = fcntl(file_desc, F_DUPFD, file_desc2);
F_GETFD Gets the value of the close-on-exec flag associated with the file descriptor file_desc. File descriptor flags are associated with a single file descriptor and do not affect other file descriptors that refer to the same file. The file_desc2 parameter should not be specified. F_SETFD Sets the close-on-exec flag associated with file_desc to the value of the third argument, taken as type int : If the third argument is 0 (zero), the file remains open across the exec functions, which means that a child process spawned by the exec function inherits this file descriptor from the parent.
If the third argument is FD_CLOEXEC, the file is closed on successful execution of the next exec function, which means that the child process spawned by the exec function will not inherit this file descriptor from the parent.
n Upon successful completion, the value returned depends on the value of the request parameter as follows:
- F_DUPFD -- Returns a new file descriptor.
- F_GETFD -- Returns FD_CLOEXEC or 0 (zero).
- F_SETFD -- Returns a value other than --1.
--1 Indicates that an error occurred. The function sets errno to the following value:
- EBADF -- The file_desc parameter is not a valid open file descriptor and the argument parameter file descriptor is negative or greater than or equal to the per-process limit.
- EFAULT -- The argument parameter is an invalid address.
- EINVAL -- The request parameter is F_DUPFD and the argument parameter is negative or greater than or equal to OPEN_MAX.
Either the OPEN_MAX value or the per-process soft descriptor limit is checked.
An illegal value was provided for the request parameter.
- EMFILE -- The request parameter is F_DUPFD and too many or OPEN_MAX file descriptors are currently open in the calling process, or no file descriptors greater than or equal to argument are available.
Either the OPEN_MAX value or the per-process soft descriptor limit is checked.
- ENOMEM -- The system was unable to allocate memory for the requested file descriptor.
Converts its argument to a null-terminated string of ASCII digits and returns the address of the string. The string is stored in a thread-specific location created by the Compaq C RTL.
#include <stdlib.h>char *fcvt (double value, int ndigits, int *decpt, int *sign);
value
An object of type double that is converted to a null-terminated string of ASCII digits.ndigits
The number of ASCII digits after the decimal point to be used in the converted string.decpt
The position of the decimal point relative to the first character in the returned string. The returned string does not contain the actual decimal point. A negative int value means that the decimal point is decpt number of spaces to the left of the returned digits (the spaces are filled with zeros). A 0 value means that the decimal point is immediately to the left of the first digit in the returned string.sign
An integer value that indicates whether the value argument is positive or negative. If value is negative, the fcvt function places a nonzero value at the address specified by sign. Otherwise, the functions assign 0 to the address specified by sign.
This function converts value to a null-terminated string and returns a pointer to it. The resulting low-order digit is rounded to the correct digit for outputting ndigits digits in C F-format. The decpt argument is assigned the position of the decimal point relative to the first character in the string.In C F-format, ndigits is the number of digits desired after the decimal point. Very large numbers produce a very long string of digits before the decimal point, and ndigit of digits after the decimal point. For large numbers, it is preferable to use the gcvt or ecvt function so that E-format is used.
Repeated calls to the fcvt function overwrite any existing string.
The ecvt , fcvt , and gcvt functions represent the following special values specified in the IEEE Standard for floating-point arithmetic:
Value Representation Quiet NaN NaNQ Signalling NaN NaNS +Infinity Infinity --Infinity --Infinity The sign associated with each of these values is stored into the sign argument. In IEEE floating-point representation, a value of 0 (zero) can be positive or negative, as set by the sign argument.
See also gcvt and ecvt in this section.
x A pointer to the converted string.
Associates a file pointer with a file descriptor returned by an open , creat , dup , dup2 , or pipe function.
#include <stdio.h>FILE *fdopen (int file_desc, char *a_mode);
file_desc
The file descriptor returned by open , creat , dup , dup2 , or pipe .a_mode
The access mode indicator. See the fopen function in this section for a description. Note that the access mode specified must agree with the mode used to open the file originally. This includes binary/text access mode ("b" mode on fdopen and the "ctx=bin" option on creat or open ).
This function allows you to access a file, originally opened by one of the UNIX I/O functions, with Standard I/O functions. Ordinarily, a file can be accessed by either a file descriptor or by a file pointer, but not both, depending on the way you open it. For more information, see Chapters 1 and 2.
pointer Indicates that the operation has succeeded. NULL Indicates that an error has occurred.
Tests a file to see if the end-of-file has been reached.
#include <stdio.h>int feof (FILE *file_ptr);
file_ptr
A file pointer.
nonzero integer Indicates that the end-of-file has been reached. 0 Indicates that the end-of-file has not been reached.
Returns a nonzero integer if an error occurred while reading or writing a file.
#include <stdio.h>int ferror (FILE *file_ptr);
file_ptr
A file pointer.
A call to ferror continues to return a nonzero integer until the file is closed or until clearerr is called.
0 Indicates success. nonzero integer Indicates that an error has occurred.
Writes out any buffered information for the specified file.
#include <stdio.h>int fflush (FILE *file_ptr);
file_ptr
A file pointer. If this argument is a NULL pointer, all buffers associated with all currently open files are flushed.
The output files are normally buffered only if they are not directed to a terminal, except for stderr, which is not buffered by default.The fflush function flushes the Compaq C RTL buffers. However, RMS has its own buffers. The fflush function does not guarantee that the file will be written to disk. (See the description of fsync for a way to flush buffers to disk.)
If the file pointed to by file_ptr was opened in record mode and if there is unwritten data in the buffer, then fflush always generates a record.
0 Indicates that the operation is successful. EOF Indicates that the buffered data cannot be written to the file, or that the file control block is not associated with an output file.
Finds the index of the first bit set in a string.
#include <strings.h>int ffs (int iteger);
integer
The integer to be examined for the first bit set.
This function finds the first bit set (beginning with the least significant bit) and returns the index of that bit. Bits are numbered starting at 1 (the least significant bit).
x The index of the first bit set. 0 If index is 0.
Returns the next character from a specified file.
#include <stdio.h>int fgetc (FILE *file_ptr);
file_ptr
A pointer to the file to be accessed.
See the getc macro in this section.
x The returned character. EOF Indicates the end-of-file or an error.
Returns the file specification associated with a file pointer.
#include <stdio.h>Function Variants This function also has variants named _fgetname32 and _fgetname64 for use with 32-bit and 64-bit pointer sizes, respectively. See Section 1.8 for more information on using pointer-size-specific functions.char *fgetname (FILE *file_ptr, char *buffer, ...);
file_ptr
A file pointer.buffer
A pointer to a character string that is large enough to hold the file specification....
An optional additional argument that can be either 1 or 0. If you specify 1, the fgetname function returns the file specification in OpenVMS format. If you specify 0, fgetname returns the file specification in UNIX style format. If you do not specify this argument, fgetname returns the file name according to your current command language interpreter. For more information about UNIX style file specifications, see Section 1.4.3.
This function places the file specification at the address given in the buffer. The buffer should be an array large enough to contain a fully qualified file specification (the maximum length is 256 characters).
n The address of the buffer. 0 Indicates an error.
This function is specific to the Compaq C RTL and is not portable.
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