Template:cpp/io/c/sidebar
| FILE *fopen( const char *filename, const char *mode ); |
|
|
| | |
Opens a file indicated by filename and returns a file stream associated with that file. mode is used to determine the file access mode.
Template:params
| filename
|
-
|
file name to associate the file stream to
|
| mode
|
-
|
null-terminated character string determining file access mode
File access
mode string
|
Meaning
|
Explanation
|
Action if file
already exists
|
Action if file
does not exist
|
| "r"
|
read
|
Open a file for reading
|
read from start
|
return NULL and set error
|
| "w"
|
write
|
Create a file for writing
|
destroy contents
|
create new
|
| "a"
|
append
|
Append to a file
|
write to end
|
create new
|
| "r+"
|
read extended
|
Open a file for read/write
|
read from start
|
return NULL and set error
|
| "w+"
|
write extended
|
Create a file for read/write
|
destroy contents
|
create new
|
| "a+"
|
append extended
|
Open a file for read/write
|
write to end
|
create new
|
File access mode flag "b" can optionally be specified to open a file in binary mode. This flag has no effect on POSIX systems, but on Windows, for example, it disables special handling of '\n' and '\x1A'.
On the append file access modes, data is written to the end of the file regardless of the current position of the file position indicator.
|
| File access mode flag "x" can optionally be appended to "w" or "w+" specifiers. This flag forces the function to fail if the file exists, instead of overwriting it. (C++17)
|
| The behavior is undefined if the mode is not one of the strings listed above. Some implementations define additional supported modes (e.g. Windows).
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|
Template:returns
opened file stream on success, Template:cpp on failure
Template:see also
