rewind() — Set file position to beginning of file
Standards
| Standards / Extensions | C or C++ | Dependencies |
|---|---|---|
ISO C
POSIX.1 XPG4 XPG4.2 C99 Single UNIX Specification, Version 3 Language Environment® |
both |
Format
#include <stdio.h>
void rewind(FILE *stream);
#define _OPEN_SYS_UNLOCKED_EXT 1
#include <stdio.h>
void rewind_unlocked(FILE *stream);General description
Repositions
the file position indicator of the stream pointed to by stream.
A call to rewind() is the same as the statement below, except that
rewind() also clears the error indicator for the stream.
(void) fseek(stream, 0L, SEEK_SET);rewind_unlocked() is functionally equivalent to rewind() with the exception that it is not thread-safe. This function can safely be used in a multithreaded application if and only if it is called while the invoking thread owns the (FILE*) object, as is the case after a successful call to either the flockfile() or ftrylockfile() function.
Returned value
rewind() returns no values.
If an error occurs, errno is set. After the error, the file position does not change. The next operation may be either a read or a write operation.
Special behavior for XPG4.2: The rewind() function returns -1 and sets errno to ESPIPE if the underlying file type for the stream is a PIPE or a socket.
Example
CELEBR14
/* CELEBR14
This example first opens a file myfile for input
and output.
It writes integers to the file, uses &rewind. to reposition
the file pointer to the beginning of the file, and then reads
the data back in.
*/
#include <stdio.h>
int main(void)
{
FILE *stream;
int data1, data2, data3, data4;
data1 = 1; data2 = -37;
/* Place data in the file */
stream = fopen("myfile.dat", "w+");
fprintf(stream, "%d %d\n", data1, data2);
/* Now read the data file */
rewind(stream);
fscanf(stream, "%d", &data3);
fscanf(stream, "%d", &data4);
printf("The values read back in are: %d and %d\n",
data3, data4);
}
Output
The values read back in are: 1 and -37