linux acpi: Extract information from /proc instead of /sys

Extracting Information from /proc in Linux ACPI

ACPI, which stands for Advanced Configuration and Power Interface, is an industry-standard protocol for power management in computers. In Linux, ACPI information is commonly accessed through a virtual file system located in the "/sys" directory. However, an alternative method exists to retrieve this information using the "/proc" directory. Let's explore how we can extract ACPI information from "/proc" in Linux.

To read ACPI information from "/proc", we can use the "procfs" interface, which exposes kernel information in a hierarchical file structure. In this example, we'll retrieve the ACPI battery status.

First, we need to access the "/proc/acpi/battery" directory, where the battery information is stored. We can accomplish this by reading the contents of the directory using the "readdir" system call. Here is the code example:

#include <stdio.h>
#include <dirent.h>

int main() {
  DIR *dir;
  struct dirent *entry;

  dir = opendir("/proc/acpi/battery");
  
  if (dir == NULL) {
    perror("Unable to open directory");
    return 1;
  }
  
  while ((entry = readdir(dir)) != NULL) {
    if (entry->d_type == DT_DIR) {
      printf("%s\n", entry->d_name);
    }
  }
  
  closedir(dir);
  
  return 0;
}

With this code, we open the "/proc/acpi/battery" directory using the opendir function. Then, we read the directory's content using the readdir function. If an entry is a directory, we print its name. Finally, we close the directory using the closedir function.

Using the "/proc" directory to extract ACPI information provides an alternative approach to accessing kernel data. It can be particularly useful if the "/sys" directory is not available or accessible for some reason.

Please note that the code example provided is a basic illustration of accessing the "/proc/acpi/battery" directory. Depending on the specific ACPI information you want to extract, you may need to read and parse different files within the "/proc" hierarchy.

Remember to always consult the official documentation and resources for a deeper understanding of the ACPI implementation in Linux and its associated file structures.

Happy coding!