LinuxQuestions.org - EOF in sysfs

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- - EOF in sysfs (https://www.linuxquestions.org/questions/linux-software-2/eof-in-sysfs-846470/)

Hi everybody,
i'm trying to write in a file (foo) using sysfs.
I'll post part of using code:

Code:

static char foo[1024];

static int baz;

static char bar[1024];



/*

 * The "foo" file where a static variable is read from and written to.

 */

static ssize_t foo_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) {        

return sprintf(buf, "%s\n\n\n\n\n\n", foo);

}



static ssize_t foo_store(struct kobject *kobj, struct kobj_attribute *attr,

                        const char *buf, size_t count)

{

        sscanf(buf, "%s", &foo);

        return count;

}



static struct kobj_attribute foo_attribute =

        __ATTR(foo, 0666, foo_show, foo_store);

I need a help. When i write a string (using echo), it seems work. When i write another one, the new one OVERWRITE the old one. Can I avoid this problem?
I note that, after writing a string, when i open the file, the cursor is positioning at the begin of the file...
Can you help me?

?WTF?

"sysfs" is essentially "/proc" and friends.

It's primarily for reading system information. And, of course, some entries are also writable (e.g. to update system configuration parameters on-the-fly).

So what exactly are you trying to do? Can you cut/paste specific code (without the "foo, bar, baz" stuff)?

PS:
Here's one example of how I'd use sysf. I'm curious how your ideas differ:

Code:

#include <stdio.h>



int

main ()

{

  FILE *fp = fopen ("/proc/cpuinfo", "r");

  if (!fp)

  {

    perror ("Unable to open /proc/cpuinfo");

    return 1;

  }

  while (!feof (fp))

  {

    char buf[80];

    char *s = fgets (buf, sizeof (buf), fp);

    if (s)

      printf(s);

  }

  fclose (fp);

  return 0;

}

Darn backkey. Wrong thread.