5.2. Top-level Files within the proc File System
5.2. Top-level Files within the proc File System Below is a list of some of the more useful virtual files in the top-level of the /proc/ directory. Note In most cases, the content of the files listed in this section are not the same as those installed on your machine. This is because much of the information is specific to the hardware on which Red Hat Enterprise Linux is running for this documentation effort. 5.2.1. /proc/apm This file provides information about the state of the Advanced Power Management (APM) system and is used by the apm command. If a system with no battery is connected to an AC power source, this virtual file would look similar to the following: Running the apm -v command on such a system results in output similar to the following: For systems which do not use a battery as a power source, apm is able do little more than put the machine in standby mode. The apm command is much more useful on laptops. For example, the following output is from the command cat /proc/apm on a laptop while plugged into a power outlet: When the same laptop is unplugged from its power source for a few minutes, the content of the apm file changes to something like the following: The apm -v command now yields more useful data, such as the following:
1.16 1.2 0x07 0x01 0xff 0x80 -1% -1 ? APM BIOS 1.2 (kernel driver 1.16ac) AC on-line, no system battery 1.16 1.2 0x03 0x01 0x03 0x09 100% -1 ? 1.16 1.2 0x03 0x00 0x00 0x01 99% 1792 min APM BIOS 1.2 (kernel driver 1.16) AC off-line, battery status high: 99% (1 day, 5:52)