/*
lseek - executable wrapper for the C lseek() function
usage: lseek fd offset origin
types: int fd; long offset; int origin;
fd can be 0 for stdin
          1 for stdout
          2 for stderr
          n for fd n
offset is the number of bytes from the origin
origin can be 0 for SEEK_SET (beginning of file)
              1 for SEEK_CUR (current position in file)
              2 for SEEK_END (end of file)

example sh usage:

	# RESTORE FD
        exec 3<<eof
	hello
	eof
	cat <&3
	cat <&3
	lseek 3 0 0
	cat <&3

	# GOTO $label
	sh <<\eof
	echo once
	loop=`lseek 0 0 1`
	echo loop
	lseek 0 $loop 0
	eof

	# GOTO
	. /dev/stdin <<\eof
	echo loop
	lseek 0 0 0 # goto echo loop
	eof

	# NOTE THAT label=$(lseek 0 0 1) DOES
        # NOT WORK WITH . /dev/stdin SO USE
        # sh <<\eof INSTEAD

see also: cat <&3 >/dev/null # lseek 3 0 2
note that dd seek does not work

*/

#include <unistd.h> /* lseek */
#include <stdio.h>

long lseek(int fd, long offset, int origin);
           int fd; long offset; int origin;

/* SEEK_SET=0; SEEK_CUR=1; SEEK_END=2; */

int main(int argc, char ** argv) {
if(argc!=4) return 1;
sscanf(argv[1], "%d", &fd);
sscanf(argv[2], "%ld", &offset);
sscanf(argv[3], "%d", &origin);
offset=lseek(fd, offset, origin);
printf("%ld\n", offset);
return offset==-1 ? 2 : 0;
}

/* can use this as a goto with . /dev/stdin <script */