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Linux / Unix Command: stdio
Command Library

NAME

stdio - standard input/output library functions  

SYNOPSIS

#include <stdio.h>

FILE *stdin;
FILE *stdout;
FILE *stderr;  

DESCRIPTION

The standard I/O library provides a simple and efficient buffered stream I/O interface. Input and output 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 append 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 output 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. Output streams are flushed (any unwritten buffer contents are transferred 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 conventional input), --- standard output (for writing conventional 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, FOPEN_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.  

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
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
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
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
vsprintf
formatted output conversion
vsscanf
input format conversion
 

CONFORMING TO

The stdio library conforms to ANSI X3.159-1989 (``ANSI C'').  

SEE ALSO

open(2), close(2), read(2), write(2), stdout(3)


Important: Use the man command (% man) to see how a command is used on your particular computer.

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