# slow5_write
## NAME
slow5_write - writes a SLOW5 record to a SLOW5 file.
## SYNOPSYS
`int slow5_write(slow5_rec_t *read, slow5_file_t *s5p)`
## DESCRIPTION
`slow5_write()` writes a SLOW5 record pointed by *read* to a SLOW5 file pointed by *s5p*.
The argument *s5p* points to a *slow5_file_t* opened using `slow5_open()` for writing or appending.
## RETURN VALUE
Upon successful completion, `slow5_write()` returns a non negative integer (>=0). Otherwise a negative value is returned.
## ERRORS
todo
## NOTES
In the future a error number will be set to indicate the error.
## EXAMPLES
```
#include <stdio.h>
#include <stdlib.h>
#include <slow5/slow5.h>
#define FILE_PATH "test.slow5"
int main(){
slow5_file_t *sp = slow5_open(FILE_PATH, "w");
if(sp==NULL){
fprintf(stderr,"Error opening file!\n");
exit(EXIT_FAILURE);
}
slow5_hdr_t* header = sp->header;
//add a header group attribute called run_id
if (slow5_hdr_add("run_id", header) != 0){
fprintf(stderr,"Error adding run_id attribute\n");
exit(EXIT_FAILURE);
}
//set the run_id attribute to "run_0" for read group 0
if (slow5_hdr_set("run_id", "run_0", 0, header) != 0){
fprintf(stderr,"Error setting run_id attribute in read group 0\n");
exit(EXIT_FAILURE);
}
if(slow5_hdr_write(sp) < 0){
fprintf(stderr,"Error writing header!\n");
exit(EXIT_FAILURE);
}
slow5_rec_t *slow5_record = slow5_rec_init();
if(slow5_record == NULL){
fprintf(stderr,"Could not allocate space for a slow5 record.");
exit(EXIT_FAILURE);
}
char *read_id = "read_1";
int16_t raw_signal[10] = {0,1,2,3,4,5,6,7,8,9}; //a raw signal of length 10
//set the field
slow5_record -> read_id = read_id;
slow5_record -> read_id_len = strlen(read_id);
slow5_record -> read_group = 0;
slow5_record -> digitisation = 4096.0;
slow5_record -> offset = 4.0;
slow5_record -> range = 12.0;
slow5_record -> sampling_rate = 4000.0;
slow5_record -> len_raw_signal = 10;
slow5_record -> raw_signal = raw_signal;
//write to file
if (slow5_write(slow5_record, sp) < 0){
fprintf(stderr,"Error writing record!\n");
exit(EXIT_FAILURE);
}
//free memory
//slow5_rec_free will attempt to free read_id and raw_signal arrays.
//As we allocated them on the stack and thus they must not be freed, we must set them to NULL before calling slow5_rec_free.
slow5_record -> read_id = NULL;
slow5_record -> raw_signal = NULL;
slow5_rec_free(slow5_record);
//close the file
slow5_close(sp);
return 0;
}
```