GETS (3)
input of characters and strings
SYNOPSIS
#include <stdio.h>
int fgetc(FILE * stream );
char *fgets(char * s , int size , FILE * stream );
int getc(FILE * stream );
int getchar(void);
char *gets(char * s );
int ungetc(int c , FILE * stream );
DESCRIPTION
fgetc()
reads the next character from
stream
and returns it as an
unsigned char
cast to an
int ,
or
EOF
on end of file or error.
getc()
is equivalent to
fgetc()
except that it may be implemented as a macro which evaluates
stream
more than once.
getchar()
is equivalent to
getc( stdin ) \fR.
gets() reads
a line from
stdin
into the buffer pointed to by
s
until either a terminating newline or
EOF ,
which it replaces with
'\e0' .
No check for buffer overrun is performed (see
BUGS
below).
fgets()
reads in at most one less than
size
characters from
stream
and stores them into the buffer pointed to by
s .
Reading stops after an
EOF
or a newline. If a newline is read, it is stored into the buffer. A
'\e0'
is stored after the last character in the buffer.
ungetc()
pushes
c
back to
stream ,
cast to
unsigned char
where it is available for subsequent read operations. Pushed - back characters
will be returned in reverse order; only one pushback is guaranteed.
Calls to the functions described here can be mixed with each other and with
calls to other input functions from the
stdio
library for the same input stream.
RETURN VALUES
fgetc() , getc() and getchar()
return the character read as an
unsigned char
cast to an
int
or
EOF
on end of file or error.
gets() and fgets()
return
s
on success, and
NULL
on error or when end of file occurs while no characters have been read.
ungetc()
returns
c
on success, or
EOF
on error.
CONFORMING TO
BUGS
Because it is impossible to tell without knowing the data in advance how many
characters
gets()
will read, and because
gets()
will continue to store characters past the end of the buffer, it is extremely
dangerous to use. It has been used to break computer security. Use
fgets()
instead.
It is not advisable to mix calls to input functions from the
stdio
library with low - level calls to
read()
for the file descriptor associated with the input stream; the results will be undefined
and very probably not what you want.
SEE ALSO
- read (2) -
- write (2) -
- fopen (3) -
- fread (3) -
- scanf (3) -
- puts (3) -
- fseek (3) -
- ferror (3) -
' " ' " Copyright(c) 1994 The Regents of the University of California ' " Copyright(c) 1994-1996 Sun Microsystems Inc ' " ' " See the file "license terms" for information on usage and redistribution ' " of this file and for a DISCLAIMER OF ALL WARRANTIES ' " ' " RCS: @(#) $Id: GetScroll 3 v 1 2 1998/09/14 18:22:51 stanton Exp $ ' " ' " The definitions below are for supplemental macros used in Tcl/Tk ' " manual entries ' " ' " AP type name in/out ?indent? ' " Start paragraph describing an argument to a library procedure ' " type is type of argument(int etc ) in/out is either "in" "out" ' " or "in/out" to describe whether procedure reads or modifies arg ' " and indent is equivalent to second arg of IP(shouldn't ever be ' " needed; use AS below instead) ' " ' " AS ?type? ?name? ' " Give maximum sizes of arguments for setting tab stops Type and ' " name are examples of largest possible arguments that will be passed ' " to AP later If args are omitted default tab stops are used ' " ' " BS ' " Start box enclosure From here until next BE everything will be ' " enclosed in one large box ' " ' " BE ' " End of box enclosure ' " ' " CS ' " Begin code excerpt ' " ' " CE ' " End code excerpt ' " ' " VS ?version? ?br? ' " Begin vertical sidebar for use in marking newly-changed parts ' " of man pages The first argument is ignored and used for recording ' " the version when the VS was added so that the sidebars can be ' " found and removed when they reach a certain age If another argument ' " is present then a line break is forced before starting the sidebar ' " ' " VE ' " End of vertical sidebar ' " ' " DS ' " Begin an indented unfilled display ' " ' " DE ' " End of indented unfilled display ' " ' " SO ' " Start of list of standard options for a Tk widget The ' " options follow on successive lines in four columns separated ' " by tabs ' " ' " SE ' " End of list of standard options for a Tk widget ' " ' " OP cmdName dbName dbClass ' " Start of description of a specific option cmdName gives the ' " option's name as specified in the class command dbName gives ' " the option's name in the option database and dbClass gives ' " the option's class in the option database ' " ' " UL arg1 arg2 ' " Print arg1 underlined then print arg2 normally ' " ' " RCS: @(#) $Id: man macros v 1 2 1998/09/14 18:39:54 stanton Exp $ ' " ' " # Set up traps and other miscellaneous stuff for Tcl/Tk man pages t wh -1 3i ^B ^l n( l b ' " # Start an argument description AP !" $4"" TP $4 { !" $2"" TP n()Cu 15
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