STDIO(O) Linux Programmer's Manual STDIO(O) 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 character- istics 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(c) function; all output takes place as if all characters were read by successive calls to the fputc(c) 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(t) function is called, all open files are closed (hence all output streams are flushed) before program ter- mination. Other methods of program termination, such as abort(t) do not bother about closing files properly. At program startup, three text streams are predefined and need not be opened explicitly -- standard input (for read- ing conventional input), -- standard output (for writing conventional input), and standard error (for writing diag- nostic output). These streams are abbreviated stdin,std- out 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(h) 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 rou- tines are automatically loaded as needed by the compilers cc(c) and pc(c). 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 defini- tions 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, std- out. Function versions of the macro functions feof, fer- ror, 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(n), close(e), read(d), write(e), stdout(t) 2001-12-26 STDIO(O)