| Types and objects | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Defined in header <stdio.h> | ||
Sets the file position indicator and the multibyte parsing state (if any) for the file streamstream according to the value pointed to bypos.
Besides establishing new parse state and position, a call to this function undoes the effects ofungetc and clears the end-of-file state, if it is set.
If a read or write error occurs, the error indicator (ferror) for the stream is set.
Contents |
| stream | - | file stream to modify |
| pos | - | pointer to afpos_t object to use as new value of file position indicator |
0 upon success, nonzero value otherwise.
After seeking to a non-end position in a wide stream, the next call to any output function may render the remainder of the file undefined, e.g. by outputting a multibyte sequence of a different length.
fsetpos with error checking
#include <stdio.h>#include <stdlib.h> int main(void){// Prepare an array of FP (floating-point) values.#define SIZE 5double A[SIZE]={1.0,2.0,3.0,4.0,5.0};// Write array to a file.FILE* fp=fopen("test.bin","wb");fwrite(A,sizeof(double),SIZE,fp);fclose(fp); // Read the FP values into array B.double B[SIZE]; fp=fopen("test.bin","rb");fpos_t pos;if(fgetpos(fp,&pos))// current position: start of file{perror("fgetpos()");fprintf(stderr,"fgetpos() failed in file %s at line # %d\n", __FILE__, __LINE__-3);exit(EXIT_FAILURE);} int ret_code=fread(B,sizeof(double),1,fp);// read one FP value// current position: after reading one f-p valueprintf("%.1f; read count = %d\n", B[0], ret_code);// print one FP value and ret_code if(fsetpos(fp,&pos))// reset current position to start of file{if(ferror(fp)){perror("fsetpos()");fprintf(stderr,"fsetpos() failed in file %s at line # %d\n", __FILE__, __LINE__-5);exit(EXIT_FAILURE);}} ret_code=fread(B,sizeof(double),1, fp);// reread first FP valueprintf("%.1f; read count = %d\n", B[0], ret_code);// print one FP value and ret_codefclose(fp); returnEXIT_SUCCESS;}
Possible output:
1.0; read count = 11.0; read count = 1
| gets the file position indicator (function)[edit] | |
| returns the current file position indicator (function)[edit] | |
| moves the file position indicator to a specific location in a file (function)[edit] | |
C++ documentation forfsetpos | |
