2 Understanding Input and Output

There are three types of input and output (I/O) in the DEC C Run-Time Library (RTL): UNIX, Standard, and Terminal. Table 2-1 lists all the I/O functions and macros found in the DEC C RTL. For more detailed information on each function and macro, see the Reference Section.

Table 2-1 I/O Functions and Macros

Function or Macro  Description 
UNIX I/O-Opening and Closing Files 
close  Closes the file associated with a file descriptor. 
creat  Creates a new file. 
dup, dup2  Allocates a new descriptor that refers to a file specified by a file descriptor returned by open, creat, or pipe. 
open  Opens a file and positions it at its beginning. 
UNIX I/O-Reading from Files 
read  Reads bytes from a file and places them in a buffer. 
UNIX I/O-Writing to Files 
write  Writes a specified number of bytes from a buffer to a file. 
UNIX I/O-Maneuvering in Files 
lseek  Positions a stream file to an arbitrary byte position and returns the new position as an int. 
UNIX I/O- Additional Standard I/O Functions and Macros 
fstat, stat  Accesses information about the file descriptor or the file specification. 
fsync  Writes to disk any buffered information for the specified file. 
getname  Returns the file specification associated with a file descriptor. 
isapipe  Returns 1 if the file descriptor is associated with a pipe and 0 if it is not. 
isatty  Returns 1 if the specified file descriptor is associated with a terminal and 0 if it is not. 
lwait  Waits for completion of pending asynchronous I/O. 
ttyname  Returns a pointer to the null-terminated name of the terminal device associated with file descriptor 0, the default input device. 
Standard I/O-Opening and Closing Files 
fclose  Closes a function by flushing any buffers associated with the file control block, and freeing the file control block and buffers previously associated with the file pointer. 
fdopen  Associates a file pointer with a file descriptor returned by an open, creat, dup, dup2, or pipe function. 
fopen  Opens a file by returning the address of a FILE structure. 
freopen  Substitutes the file, named by a file specification, for the open file addressed by a file pointer. 
Standard I/O-Reading from Files 
fgetc, getc, getw, getwc  Returns characters from a specified file. 
fgets, fgetws  Reads a line from a specified file and stores the string in an argument. 
fread  Reads a specified number of items from a file. 
fscanf, fwscanf  Performs formatted input from a specified file. 
sscanf, swscanf  Performs formatted input from a character string in memory. 
ungetc, ungetwc  Pushes back a character into the input stream and leaves the stream positioned before the character. 
Standard I/O-Writing to Files 
fprintf, fwprintf, vfprintf, vfwprintf  Performs formatted output to a specified file. 
fputc, putc, putw, putwc  Writes characters to a specified file. 
fputs, fputws  Writes a character string to a file without copying the string's null terminator. 
fwrite  Writes a specified number of items to a file. 
sprintf, swprintf, vsprintf, vswprintf  Performs formatted output to a string in memory. 
Standard I/O-Maneuvering in Files 
fflush  Sends any buffered information for the specified file to RMS. 
fgetpos  Stores the current value of the file position indicator for the stream. 
fsetpos  Sets the file position indicator for the stream according to the value of the object pointed to. 
fseek  Positions the file to the specified byte offset in the file. 
ftell  Returns the current byte offset to the specified stream file. 
rewind  Sets the file to its beginning. 
Standard I/O-Additional Standard I/O Functions and Macros 
access  Checks a file to see whether a specified access mode is allowed. 
clearerr  Resets the error and end-of-file indications for a file. 
feof  Tests a file to see if the end-of- file has been reached. 
ferror  Returns a nonzero integer if an error has occurred while reading or writing a file. 
fgetname  Returns the file specification associated with a file pointer. 
fileno  Returns an integer file descriptor that identifies the specified file. 
fwait  Waits for completion of pending asynchcronous I/O. 
fwide  Sets the orientation a stream. 
mktemp  Creates a unique file name from a template. 
remove, delete  Deletes a file. 
rename  Gives a new name to an existing file. 
setbuf, setvbuf  Associates a buffer with an input or output file. 
tmpfile  Creates a temporary file that is opened for update. 
tmpnam  Creates a character string that can be used in place of the file-name argument in other function calls. 
Terminal I/O-Reading from Files 
getchar, getwchar  Reads a single character from the standard input (stdin). 
gets  Reads a line from the standard input (stdin). 
scanf, wscanf  Performs formatted input from the standard input. 
Terminal I/O-Writing to Files 
printf, wprintf, vprintf, vwprintf  Performs formatted output to the standard output (stdout). 
putchar, putwchar  Writes a single character to the standard output and returns the character. 
puts  Writes a character string to the standard output followed by a new-line character. 


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