NAME

       scanf, fscanf, vscanf, vfscanf - input FILE format conversion

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <stdio.h>

       int scanf(const char *restrict format, ...);
       int fscanf(FILE *restrict stream,
                  const char *restrict format, ...);

       #include <stdarg.h>

       int vscanf(const char *restrict format, va_list ap);
       int vfscanf(FILE *restrict stream,
                  const char *restrict format, va_list ap);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       vscanf(), vfscanf():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION

       The  scanf()  family  of  functions  scans formatted input like sscanf(3), but read from a
       FILE.  It is very difficult to use these functions correctly, and it is preferable to read
       entire  lines  with  fgets(3)  or  getline(3)  and parse them later with sscanf(3) or more
       specialized functions such as strtol(3).

       The scanf() function reads input from the standard input stream stdin and  fscanf()  reads
       input from the stream pointer stream.

       The vfscanf() function is analogous to vfprintf(3) and reads input from the stream pointer
       stream using a variable argument list of pointers (see stdarg(3).  The  vscanf()  function
       is analogous to vprintf(3) and reads from the standard input.

RETURN VALUE

       On  success,  these  functions  return  the number of input items successfully matched and
       assigned; this can be fewer than provided for, or even zero, in  the  event  of  an  early
       matching failure.

       The  value  EOF  is  returned  if  the  end  of  input  is reached before either the first
       successful conversion or a matching failure occurs.  EOF is also returned if a read  error
       occurs, in which case the error indicator for the stream (see ferror(3)) is set, and errno
       is set to indicate the error.

ERRORS

       EAGAIN The file descriptor underlying stream is marked nonblocking, and the read operation
              would block.

       EBADF  The file descriptor underlying stream is invalid, or not open for reading.

       EILSEQ Input byte sequence does not form a valid character.

       EINTR  The read operation was interrupted by a signal; see signal(7).

       EINVAL Not enough arguments; or format is NULL.

       ENOMEM Out of memory.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌────────────────────────────────────────────────────────┬───────────────┬────────────────┐
       │Interface                                               │ Attribute     │ Value          │
       ├────────────────────────────────────────────────────────┼───────────────┼────────────────┤
       │scanf(), fscanf(), vscanf(), vfscanf()                  │ Thread safety │ MT-Safe locale │
       └────────────────────────────────────────────────────────┴───────────────┴────────────────┘

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       C99, POSIX.1-2001.

CAVEATS

       These  functions make it difficult to distinguish newlines from other white space, This is
       especially problematic with line-buffered input, like the standard input stream.

       These  functions  can't  report  errors   after   the   last   non-suppressed   conversion
       specification.

BUGS

       It is impossible to accurately know how many characters these functions have consumed from
       the input stream, since they only  report  the  number  of  successful  conversions.   For
       example,  if  the  input is "123\n a", scanf("%d %d", &a, &b) will consume the digits, the
       newline, and the space, but not the letter a.  This makes it  difficult  to  recover  from
       invalid input.

SEE ALSO

       fgets(3), getline(3), sscanf(3)