GpioUnExport.c

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#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include "../Sysfs/Sysfs.h"
#include "../config.h"

#define BUFFER_MAX 3 /* pin 0 .. 99 and a trailing zero */

int GpioUnExport(int Pin)
 {
 char buffer[BUFFER_MAX];
 ssize_t BytesToWrite;
 ssize_t BytesWritten;
 int fd;
 
 fd = open("/sys/class/gpio/unexport", O_WRONLY);
 if (fd == -1) 
  {
  fprintf(stderr, "201309202231 Failed to open unexport for writing, are you root?\n");
  return(-1);
  }
 
 BytesToWrite = snprintf(buffer, BUFFER_MAX, "%d", Pin);
 BytesWritten = write(fd, buffer, BytesToWrite);

 if( BytesWritten != BytesToWrite )
  {
  fprintf( stderr, "201309210100 Encountered short write\n" );
  fprintf( stderr, "201309231033 BytesToWrite was %i, BytesWritten was %i\n", (int)BytesToWrite, (int)BytesWritten );
  return(-2);
  }

 close(fd);
 return(0);
 }