DEC C
Language Reference Manual
Power Functions
double pow(double x, double
y);
- Returns the value xy. A domain error
occurs if x is negative and y is not an integral
value. A domain error occurs if the result cannot be represented when
x is 0 and y is less than or equal to 0. A range
error may occur.
double sqrt(double x);
- Returns the nonnegative square root of x. A domain error
occurs if x is negative.
Nearest Integer, Absolute Value, and Remainder
Functions
double ceil(double x);
- Returns the smallest integral value not less than x.
double fabs(double x);
- Returns the absolute value of a floating-point number x.
double floor(double x);
- Returns the largest integral value not greater than x.
double fmod(double x, double
y);
- Computes the floating-point remainder of x/y. The
fmod function returns the value
x -- i * y, for some integer i such
that if y is nonzero, the result has the same sign as
x and magnitude less than the magnitude of y. The
function returns 0 if y is 0.
9.7 Nonlocal Jumps (<setjmp.h>)
The <setjmp.h> header file contains
declarations that provide a way to avoid the normal function call and
return sequence, typically to permit an intermediate return from a
nested function call.
Macro
int setjmp(jmp_buf env)
- Sets up the local jmp_buf buffer and
initializes it for the jump (the jump itself is performed with longjmp.) This macro saves the program's
calling environment in the environment buffer specified by the
env argument for later use by the longjmp function. If the return is from a
direct invocation, setjmp returns 0. If
the return is from a call to longjmp,
setjmp returns a nonzero value.
Type
jmp_buf
- An array type suitable for holding the information needed to
restore a calling environment.
Function
- Restores the context of the environment buffer env that
was saved by invocation of the setjmp
function in the same invocation of the program. The longjmp function does not work if called from a
nested signal handler; the result is undefined.
The value specified
by value is passed from longjmp
to setjmp. After longjmp is completed, program execution
continues as if the corresponding invocation of setjmp had just returned value. If
value is passed to setjmp as 0,
it is converted to 1.
9.8 Signal Handling (<signal.h>)
The <signal.h> header file declares
a type and two functions and defines several macros for handling
exception conditions that might be reported during program execution.
Type
sig_atomic_t
- The integral type of an object that can be accessed as an atomic
entity, even in the presence of asynchronous interrupts.
Macros
SIG_DFL
SIG_ERR
SIG_IGN
- Expand to constant expressions with distinct values that have a
type compatible with the second argument to, and the return value of,
the signal function, and whose value
compares unequal to the address of any declarable function.
Functions
void (*signal(int sig, void (*handler) (int)))
(int);
- Determines how subsequent signals are handled. Signals are handled
in the following way:
- If the value of handler is SIG_DFL, default handling of that signal occurs.
- If the value of handler is SIG_IGN, the signal is ignored.
- Otherwise, when that signal occurs, a function pointed to by handler is called with the argument of the type
of signal. Such a function is called a signal handler. Valid
signals include:
- SIGABRT---abnormal termination, such as from the abort function
- SIGFPE---arithmetic error, such as zero divide or overflow
- SIGILL---invalid function image, such as an invalid instruction
- SIGINT---interactive attention, such as an interrupt
- SIGSEGV---invalid access to storage, such as outside of memory limit
- SIGTERM---termination request sent to the program
Any other signals are operating-system dependent.
If the
request can be honored, the signal
function returns the value of handler for
the most recent call to signal for the
specified signal sig. Otherwise, a value
of SIG_ERR is returned and an
implementation-defined positive value is stored in errno.
int raise(int sig);
- Sends the signal sig to the executing
program. The raise function returns 0 if
successful and nonzero if unsuccessful.
9.9 Variable Arguments (<stdarg.h>)
The <stdarg.h> header file declares
a type and defines three macros for advancing through a list of
function arguments of varying number and type.
Type
va_list
- A type suitable for holding information needed by the macros va_start, va_arg,
and va_end.
To access varying
arguments, the called function must declare an object (referred to as
ap in this section) that has the type va_list:
The object ap can be passed as an argument to another
function. If that function invokes the va_arg macro with parameter ap, the
value of ap in the calling function is indeterminate and is
passed to the va_end macro before any
further reference to ap.
Macros
void va_start(va_list ap,
parmN);
- Initializes ap for subsequent use by va_arg and va_end. The va_start macro must be invoked before any
access to the unnamed arguments.
The parameter parmN is
the identifier of the rightmost parameter in the variable parameter
list of the function definition. If parmN is declared with the
register storage class, with a function
or array type, or with a type that is not compatible with the type that
results after application of the default arguments promotions, the
behavior is undefined. The va_start macro
returns no value.
type va_arg(va_list ap,
type);
- Expands to an expression that has the type and value of the next
argument in the call. The parameter ap is the same as the
va_list ap that was initialized
by va_start. Each invocation of va_arg modifies ap so that the values
of successive arguments are returned in turn. The parameter
type is a type name specified such that the type of a pointer
to an object that has the specified type can be obtained by postfixing
an asterisk (*) to type. The behavior is undefined if there is
no actual next argument, or if type is not compatible with the
type of the next actual argument (as promoted according to the default
argument promotions).
The first invocation of va_arg after that of va_start returns the value of the argument
after that specified by parmN. Successive invocations return
the values of the remaining arguments in turn.
void va_end(va_list ap);
- Facilitates a normal return from the function whose variable
argument list was referred to by the expansion of va_start that initialized the va_list ap object. The va_end macro can modify ap so that it
can no longer be used (without an intervening invocation of va_start). If there is no corresponding
invocation of va_start or if va_end is not invoked before the return, the
behavior is undefined. The va_end macro
returns no value.
9.10 Common Definitions (<stddef.h>)
The <stddef.h> header file defines
several types and macros, some of which are also defined in other
header files.
Types
ptrdiff
- A signed integral type of the result of subtracting two pointers.
size_t
- An unsigned integral type of the result of the sizeof operator.
wchar_t
- An integral type whose range of values can represent distinct codes
for all members of the largest extended character set specified among
the supported locales.
Macros
NULL
- Expands to an implementation-defined null pointer constant.
offsetof(type, member-designator)
- Expands to an integral constant expression that has type size_t and a value that is the offset, in
bytes, to the structure member (specified by
member-designator) from the beginning of its structure
(specified by type). The member-designator is such
that the expression &(t.member-designator) evaluates
to an address constant given the following:
If the specified member is a bit field, the behavior is undefined.
9.11 Standard Input/Output (<stdio.h>)
The <stdio.h> header file declares
three types, several macros, and many functions for performing text
input and output. A text stream consists of a sequence of lines; each
line ends with a new-line character.
Types
size_t
- An unsigned integral type of the result of the sizeof operator.
FILE
- An object type capable of recording all the information needed to
control a data stream, including its file-position indicator, a pointer
to its associated buffer (if any), an error indicator that
records whether a read/write error occurred, and an
end-of-file indicator that records whether the end of the file
has been reached.
fpos_t
- An object capable of recording all the information needed to
uniquely specify every position within a file.
Macros
NULL
- Expands to an implementation-defined null pointer constant.
_IOFBF
_IOLBF
_IONBF
- Expand to integral constant expressions with distinct values,
suitable for use as the third argument to the setvbuf function.
BUFFSIZ
- Expands to an integral constant expression, which is the size of
the buffer used by the setbuf function.
EOF
- Expands to a negative integral constant expression that is returned
by several functions to indicate end-of-file.
FOPEN_MAX
- Expands to an integral constant expression that is the minimum
number of files that the DEC C compiler for your system
guarantees can be open simultaneously.
FILENAME_MAX
- Expands to an integral constant expression that is the size needed
for an array of char large enough to hold
the longest file name string that the DEC C compiler for your
system guarantees can be opened.
L_tmpnam
- Expands to an integral constant expression that is the size needed
for an array of char large enough to hold
a temporary file name string generated by the tmpnam function.
SEEK_CUR
SEEK_END
SEEK_SET
- Expand to integral constant expressions with distinct values;
suitable for use as the third argument to the fseek function.
TMP_MAX
- Expands to an integral constant expression that is the minimum
number of unique file names that can be generated by the tmpnam function.
stderr
stdin
stdout
- Expressions of type pointer to FILE that point to the FILE objects associated, respectively, with the
standard error, input, and output streams.
File Operation Functions
int remove(const char *filename);
- Makes the file whose name is pointed to by filename no
longer accessible by that name. Any subsequent attempt to open that
file using that name will fail. The remove function returns 0 if the operation
succeeds, nonzero if it fails. If the file is open, the behavior of
this function is implementation-defined.
int rename(const char *old, const char
*new);
- Renames the file from the name pointed to by old to the
name pointed to by new. The file is no longer accessible by
the old name. The rename function returns
0 if the operation succeeds, nonzero if it fails (in which case the
file, if it existed, is still known by its original name). If the new
file exists before rename is called, the
behavior of this function is implementation-defined.
FILE *tmpfile(void);
- Creates a temporary binary file that is automatically removed when
it is closed or when program execution ends. If execution ends
abnormally, whether an open temporary file is removed is
implementation-dependent. The file is opened for update with wb+ mode (see Table 9-1). The tmpfile function returns a pointer to the
stream of the file that it created. If the file cannot be created,
tmpfile returns a null pointer.
FILE *tmpnam(void);
- Generates a valid file name that is different than the name of an
existing file. Each call to tmpnam, up to
TMP_MAX times, generates a different
name. If tmpnam is called more than TMP_MAX times, the behavior is
implementation-defined.
If the argument is a null pointer, the
tmpnam function leaves its result in an
internal static object and returns a pointer to that object. Subsequent
calls to tmpnam can modify the same
object. If the argument is not a null pointer, it is assumed to point
to an array of at least L_tmpnam chars.
The tmpnam function writes its result
into that array and returns the argument as its value.
File Access Functions
int fclose(FILE *stream);
- Flushes the stream pointed to by stream and closes the
associated file. Any unwritten buffered data for the stream is
delivered to the host environment to be written to the file. Any unread
buffered data is discarded. The stream is disassociated from the file.
If the associated buffer was automatically allocated, it is
deallocated. The fclose function returns
0 if the stream was successfully closed, or it returns EOF if any errors are detected.
int fflush(FILE *stream);
- If stream points to an output stream or an update stream
in which the most recent operation was not input, the fflush function delivers any unwritten data to
the host environment to be written to the file. Otherwise, the behavior
is undefined. If stream is a null pointer, fflush flushes all output or update streams in
which the most recent operation was not input. The fflush function returns 0 if the operation is
successful, or it returns EOF if a write
error occurs.
FILE *fopen(const char *filename, const char
*mode);
- Opens the file pointed to by filename and associates a
stream with it. The argument mode points to a string beginning
with one of the character sequences listed in Table 9-1. Additional
characters can follow these sequences.
Table 9-1 File Modes
Mode |
Description |
r
|
open text file for reading
|
w
|
truncate to zero length or create text file for writing
|
a
|
append; open or create text file for writing at end-of-file
|
rb
|
open binary file for reading
|
wb
|
truncate to zero length or create binary file for writing
|
ab
|
append; open or create binary file for writing at end-of-file
|
r+
|
open text file for update (reading and writing)
|
w+
|
truncate to zero length or create text file for update
|
a+
|
append; open or create text file for update, writing at end-of-file
|
r+b
or rb+
|
open binary file for update (reading and writing)
|
w+b
or wb+
|
truncate to zero length or create binary file for update
|
a+b
or ab+
|
append; open or create binary file for update, writing at end-of-file
|
The fopen function returns a pointer
to the object controlling the stream. If the open operation fails,
fopen returns a null pointer.
FILE *freopen(const char *filename, const
char *mode, FILE *stream);
- Opens the file pointed to by filename and associates the
stream pointed to by stream with it. The mode
argument is used in the same way as with the fopen function. The freopen function first tries to close any file
associated with the specified stream. Failure to close the file
successfully is ignored. The error and end-of-file indicators for the
stream are cleared.
The primary use of freopen is to change the file associated with a
standard text stream (stderr, stdin, or stdout), because those identifiers need not be
modifiable lvalues to which the value returned by the fopen function can be assigned.
The freopen function returns a pointer to the
object controlling the stream. If the open operation fails, freopen returns a null pointer.
void setbuf(FILE *stream, char
*buf);
- Except that it returns no value, the setbuf function is equivalent to the setvbuf function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
is a null pointer) with the value _IONBF
for mode.
int setvbuf(FILE *stream, char
*buf, int mode size_t size);
- Associates a buffer with an input or an output file. The setvbuf function can be used only after the
stream pointed to by stream has been associated with an open
file and before any other operation is performed on the stream. The
argument mode determines how stream is to be buffered:
- IOFBF causes I/O to be fully buffered.
- IOLBF causes I/O to be line buffered.
- IONBF causes I/O to be unbuffered.
If buf is not a null pointer, the array it points to can
be used instead of a buffer allocated by the setvbuf function. The size of the array is
specified by size. The contents of the array at any time are
indeterminate. The setvbuf function
returns 0 if successful, or nonzero if an invalid value is specified
for mode or if the request cannot be honored.
Formatted Input/Output Functions
int fprintf(FILE *stream, const char
*format, ...);
- Writes output to the stream pointed to by stream, under
control of the string pointed to by format, which specifies
how subsequent arguments are converted for output. If there are an
insufficient number of arguments for the format, the behavior is
undefined. If the format is exhausted while arguments remain, the
excess arguments are evaluated but are otherwise ignored. The fprintf function returns when the end of the
format string is encountered. The fprintf
function returns the number of characters transmitted, or it returns a
negative value if an output error occurred.
See your DEC C
library routine documentation for more information.