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Write elements to a file
#include <stdio.h>
size_t fwrite( const void* buf,
size_t size,
size_t num,
FILE* fp );
- buf
- A pointer to a buffer that contains the elements that you want to write.
- size
- The size of each element to write.
- num
- The number of elements to write.
- fp
- The stream to which to write the elements.
libc
Use the -l c option to
qcc
to link against this library.
This library is usually included automatically.
The fwrite() function writes num elements of
size bytes each to the stream specified by fp.
The number of complete elements successfully written; if an error occurs,
this is less than num.
If an error occurs, errno
is set to indicate the type of error.
#include <stdio.h>
#include <stdlib.h>
struct student_data {
int student_id;
unsigned char marks[10];
};
int main( void )
{
FILE *fp;
struct student_data std;
int i;
fp = fopen( "file", "w" );
if( fp != NULL ) {
std.student_id = 1001;
for( i = 0; i < 10; i++ ) {
std.marks[i] = (unsigned char)(85 + i);
}
/* write student record with marks */
i = fwrite( &std, sizeof( struct student_data ), 1, fp );
printf( "Successfully wrote %d records\n", i );
fclose( fp );
if( i == 1 ) {
return EXIT_SUCCESS;
}
}
return EXIT_FAILURE;
}
ANSI,
POSIX 1003.1
Safety: | |
Cancellation point |
Yes |
Interrupt handler |
No |
Signal handler |
No |
Thread |
Yes |
errno,
ferror(),
fopen()
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