注意区分
gets, fgets, fgetc, getc, getchar
puts, fputs, fputc, putc, putchar
fgets
function
<cstdio>
char * fgets ( char * str, int num, FILE * stream );
Get string from stream
Reads characters from
stream
and stores them as a C string into
str
until (
num
-1) characters have been read or either a newline or a the End-of-File is reached, whichever comes first.
A newline character makes
fgets
stop reading, but it is considered a valid character and therefore it is included in the string copied to
str
.
A null character is automatically appended in
str
after the characters read to signal the end of the C string.
<cstdio>
int fputs ( const char * str, FILE * stream );
Write string to stream
Writes the string pointed by
str to the
stream.
The function begins copying from the address specified (
str) until it reaches the terminating null character ('\0').
This final null-character is not copied to the stream.
<cstdio>
int fgetc ( FILE * stream );
Get character from stream
Returns the character currently pointed by the internal file position indicator of the specified
stream. The internal file position indicator is then advanced by one character to point to the next character.
fgetc and
getc are equivalent, except that the latter one may be implemented as a macro.
Parameters
-
stream
-
Pointer to a
FILE object that identifies the stream on which the operation is to be performed.
Return Value
The character read is returned as an
int value.
If the End-of-File is reached or a reading error happens, the function returns
EOF and the corresponding error or eof indicator is set. You can use either
ferror or
feof to determine whether an error happened or the End-Of-File was reached.
<cstdio>
int fputc ( int character, FILE * stream );
Write character to stream
Writes a character to the
stream and advances the position indicator.
The character is written at the current position of the
stream as indicated by the internal position indicator, which is then advanced one character.
Parameters
-
character
-
Character to be written. The character is passed as its
int promotion.
-
stream
-
Pointer to a
FILE object that identifies the stream where the character is to be written.
Return Value
If there are no errors, the same character that has been written is returned.
If an error occurs,
EOF is returned and the error indicator is set (see
ferror).
<cstdio>
int getc ( FILE * stream );
Get character from stream
Returns the character currently pointed by the internal file position indicator of the specified
stream. The internal file position indicator is then advanced by one character to point to the next character.
getc is equivalent to
fgetc and also expects a
stream as parameter, but
getc may be implemented as a macro, so the argument passed to it should not be an expression with potential side effects.
See
getchar for a similar function without
stream parameter.
Parameters
-
stream
-
pointer to a
FILE object that identifies the stream on which the operation is to be performed.
Return Value
The character read is returned as an
int value.
If the End-of-File is reached or a reading error happens, the function returns
EOF and the corresponding error or eof indicator is set. You can use either
ferror or
feof to determine whether an error happened or the End-Of-File was reached.
<cstdio>
int putc ( int character, FILE * stream );
Write character to stream
Writes a character to the
stream and advances the position indicator.
The character is written at the current position of the
stream as indicated by the internal position indicator, which is then advanced one character.
putc is equivalent to
fputc and also expects a
stream as parameter, but
putc may be implemented as a macro, so the argument passed should not be an expression with potential side effects.
See
putchar for a similar function without
stream parameter.
Returns the next character from the standard input (stdin).
It is equivalent to
getc with
stdin as its argument.
<cstdio>
int putchar ( int character );
Write character to stdout
Writes
character to the current position in the standard output (stdout) and advances the internal file position indicator to the next position.
It is equivalent to
putc(
character,
stdout).
<cstdio>
int ferror ( FILE * stream );
Check error indicator
Checks if the error indicator associated with
stream is set, returning a value different from zero if it is.
This indicator is generaly set by a previous operation on the
stream that failed.
<cstdio>
int feof ( FILE * stream );
Check End-of-File indicator
Checks whether the End-of-File indicator associated with
stream is set, returning a value different from zero if it is.
This indicator is generally set by a previous operation on the
stream that reached the End-of-File.
Further operations on the stream once the End-of-File has been reached will fail until either
rewind,
fseek or
fsetpos is successfully called to set the position indicator to a new value.
The standard input stream is the default source of data for applications. It is usually directed to the input device of the standard console (generally, a keyboard).
stdin
can be used as an argument for any function that expects an input stream as one of its parameters, like
fgets
or
fscanf
.
The standard output stream is the default destination of regular output for applications. It is usually directed to the output device of the standard console (generally, the screen).
stdout
can be used as an argument for any function that expects an output stream as one of its parameters, like
fputs
or
fprintf
.
It is a macro constant definition. It expands to a negative integral constant expression.
It is used as the value returned by several
<cstdio> functions to indicate failure, either because the End-of-File has been reached in a reading operation
or because an error happened.
<cstdio>
FILE * fopen ( const char * filename, const char * mode );
Open file
Opens the file whose name is specified in the parameter
filename and associates it with a stream that can be identified in future operations by the FILE object whose pointer is returned. The operations that are allowed on the stream and how these are performed are defined by the
mode parameter.
The running environment supports at least
FOPEN_MAX files open simultaneously;
FOPEN_MAX is a macro constant defined in
<cstdio>.
Parameters
-
filename
-
C string containing the name of the file to be opened. This paramenter must follow the file name specifications of the running environment and can include a path if the system supports it.
-
mode
-
C string containing a file access modes. It can be:
| "r" |
Open a file for reading. The file must exist. |
| "w" |
Create an empty file for writing. If a file with the same name already exists its content is erased and the file is treated as a new empty file. |
| "a" |
Append to a file. Writing operations append data at the end of the file. The file is created if it does not exist. |
| "r+" |
Open a file for update both reading and writing. The file must exist. |
| "w+" |
Create an empty file for both reading and writing. If a file with the same name already exists its content is erased and the file is treated as a new empty file. |
| "a+" |
Open a file for reading and appending. All writing operations are performed at the end of the file, protecting the previous content to be overwritten. You can reposition (fseek, rewind) the internal pointer to anywhere in the file for reading, but writing operations will move it back to the end of file. The file is created if it does not exist. |
-
<cstdio>
int fclose ( FILE * stream );
Close file
Closes the file associated with the stream and disassociates it.
All internal buffers associated with the stream are flushed: the content of any unwritten buffer is written and the content of any unread buffer is discarded.
Even if the call fails, the stream passed as parameter will no longer be associated with the file.
Parameters
-
stream
-
Pointer to a
FILE object that specifies the stream to be closed.
Return Value
If the stream is successfully closed, a zero value is returned.
On failure, EOF is returned.
