STDIO

Section: C Library Functions (3)
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BSD mandoc
BSD 4  

NAME

stdio - standard input/output library functions  

SYNOPSIS

Fd #include <stdio.h> Fd FILE *stdin; Fd FILE *stdout; Fd FILE *stderr;  

DESCRIPTION

The standard I/O library provides a simple and efficient buffered stream I/O interface. Input and ouput is mapped into logical data streams and the physical I/O characteristics are concealed. The functions and macros are listed below; more information is available from the individual man pages.

A stream is associated with an external file (which may be a physical device) by opening a file, which may involve creating a new file. Creating an existing file causes its former contents to be discarded. If a file can support positioning requests (such as a disk file, as opposed to a terminal) then a file position indicator associated with the stream is positioned at the start of the file (byte zero), unless the file is opened with appened mode. If append mode is used, the position indicator will be placed the end-of-file. The position indicator is maintained by subsequent reads, writes and positioning requests. All input occurs as if the characters were read by successive calls to the fgetc(3) function; all ouput takes place as if all characters were read by successive calls to the fputc(3) function.

A file is disassociated from a stream by closing the file. Ouput streams are flushed (any unwritten buffer contents are transfered to the host environment) before the stream is disassociated from the file. The value of a pointer to a FILE object is indeterminate after a file is closed (garbage).

A file may be subsequently reopened, by the same or another program execution, and its contents reclaimed or modified (if it can be repositioned at the start). If the main function returns to its original caller, or the exit(3) function is called, all open files are closed (hence all output streams are flushed) before program termination. Other methods of program termination, such as abort(3) do not bother about closing files properly.

At program startup, three text streams are predefined and need not be opened explicitly --- standard input (for reading converntional input), --- standard output (for writing converntional input), and standard error (for writing diagnostic output). These streams are abbreviated stdin , stdout and stderr When opened, the standard error stream is not fully buffered; the standard input and output streams are fully buffered if and only if the streams do not to refer to an interactive device.

Output streams that refer to terminal devices are always line buffered by default; pending output to such streams is written automatically whenever an input stream that refers to a terminal device is read. In cases where a large amount of computation is done after printing part of a line on an output terminal, it is necessary to fflush(3) the standard output before going off and computing so that the output will appear.

The stdio library is a part of the library libc and routines are automatically loaded as needed by the compilers cc(1) and pc(1). The SYNOPSIS sections of the following manual pages indicate which include files are to be used, what the compiler declaration for the function looks like and which external variables are of interest.

The following are defined as macros; these names may not be re-used without first removing their current definitions with #undef BUFSIZ EOF FILENAME_MAX L_cuserid L_ctermid L_tmpnam, NULL SEEK_END SEEK_SET SEE_CUR TMP_MAX clearerr feof ferror fileno fropen fwopen getc getchar putc putchar stderr stdin stdout Function versions of the macro functions feof, ferror, clearerr, fileno, getc, getchar, putc, and putchar exist and will be used if the macros definitions are explicitly removed.  

SEE ALSO

open(2), close(2), read(2), write(2)  

BUGS

The standard buffered functions do not interact well with certain other library and system functions, especially vfork and abort.  

STANDARDS

The stdio library conforms to St -ansiC .  

LIST OF FUNCTIONS

Function       Description clearerr   check and reset stream status
fclose  close a stream
fdopen  stream open functions
feof    check and reset stream status
ferror  check and reset stream status
fflush  flush a stream
fgetc   get next character or word from input stream
fgetline        get a line from a stream
fgetpos reposition a stream
fgets   get a line from a stream
fileno  check and reset stream status
fopen   stream open functions
fprintf formatted output conversion
fpurge  flush a stream
fputc   output a character or word to a stream
fputs   output a line to a stream
fread   binary stream input/output
freopen stream open functions
fropen  open a stream
fscanf  input format conversion
fseek   reposition a stream
fsetpos reposition a stream
ftell   reposition a stream
funopen open a stream
fwopen  open a stream
fwrite  binary stream input/output
getc    get next character or word from input stream
getchar get next character or word from input stream
gets    get a line from a stream
getw    get next character or word from input stream
mktemp  make temporary file name (unique)
perror  system error messages
printf  formatted output conversion
putc    output a character or word to a stream
putchar output a character or word to a stream
puts    output a line to a stream
putw    output a character or word to a stream
remove  remove directory entry
rewind  reposition a stream
scanf   input format conversion
setbuf  stream buffering operations
setbuffer       stream buffering operations
setlinebuf      stream buffering operations
setvbuf stream buffering operations
snprintf        formatted output conversion
sprintf formatted output conversion
sscanf  input format conversion
strerror        system error messages
sys_errlist     system error messages
sys_nerr        system error messages
tempnam temporary file routines
tmpfile temporary file routines
tmpnam  temporary file routines
ungetc  un-get character from input stream
vfprintf        formatted output conversion
vfscanf input format conversion
vprintf formatted output conversion
vscanf  input format conversion
vsnprintf       formatted output conversion
vsprintf        formatted output conversion
vsscanf input format conversion


 

Index

NAME
SYNOPSIS
DESCRIPTION
SEE ALSO
BUGS
STANDARDS
LIST OF FUNCTIONS

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Time: 06:40:35 GMT, May 19, 2025