ungetc(3)



GETS(3)                    Linux Programmer's Manual                   GETS(3)

NAME
       fgetc,  fgets,  getc,  getchar,  gets, ungetc - 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).

       gets() reads a line from stdin into the buffer pointed to  by  s  until
       either  a  terminating newline or EOF, which it replaces with '\0'.  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 '\0' 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.

       For non-locking counterparts, see unlocked_stdio(3).

RETURN VALUE
       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
       C89, C99.  LSB deprecates gets().

BUGS
       Never use gets().  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  associ-
       ated  with  the  input  stream;  the results will be undefined and very
       probably not what you want.

SEE ALSO
       read(2), write(2), ferror(3), fgetwc(3), fgetws(3), fopen(3), fread(3),
       fseek(3),   getline(3),  getwchar(3),  puts(3),  scanf(3),  ungetwc(3),
       unlocked_stdio(3)

GNU                               1993-04-04                           GETS(3)

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