sf_file(3)

NAME
initfdpos, initFILEpos, adjfdpos, adjFILEpos - file positions indicator handling

SYNOPSIS
#include <stdio.h>
#include <strfunc.h>

int
initfdpos(const char *fname, int stream, const char *ext);
int
initFILEpos(const char *fname, FILE *stream, const char *ext);
int
adjfdpos(int stream, int posfd, int doSync);
int
adjFILEpos(FILE *stream, int posfd, int doSync);

DESCRIPTION
Those functions are used to maintain a file positions indicator between the program sessions. This is often needed when a process is being parsed a log file and tries to save current position within this log to start from this point later.

int initfdpos(const char *fname, int stream, const char *ext) creates a position indicator file "<fname>.<ext>", and returns its file descriptor. If the position file is already exists, then it advances stream's position according to the information derived from that file. initfdpos also checks the file size and inode changes in order to be robust in situations when file shrinked or replaced.

int initFILEpos() is almost the same except that it takes a FILE * argument instead of plain file descriptor.

Both functions returns position file descriptor, or -1 in case of failure.

int adjfdpos(int stream, int posfd, int doSync) and adFILEdpos() writes the current position within the file referenced by stream into the posfd. If doSync is not zero, it also does fsync(2). Return values: 0 (Success) or -1 in case of any errors.

EXAMPLE

    void main() {
    	int posfd;
    	FILE *logfile;
    	char buf[1042];
    	logfile = fopen("file.log", "r");
    	if(!logfile)
    		exit(EX_NOINPUT);
    	while(fgets(buf, sizeof(buf), logfile)) {
    		/* Do something ... */
    		adjFILEpos(logfile, posfd, 0);
    	};
    	/* Force data to be flushed on disk. */
    	adjFILEpos(logfile, posfd, 1);
    	fclose(logfile);
    	close(posfd);
    };

SEE ALSO
strfunc(3).

AUTHORS
Lev Walkin <vlm@spelio.net.ru>