/etc/lsb-release File Format

The /etc/lsb-release file is used in CrOS to hold some system settings. Unfortunately, nowhere is the format of this file actually documented. LSB itself only documents the lsb_release program.

Since we rely upon this file currently, we'll document the format that CrOS tooling can rely upon, and provide some language examples.

Usage

The /etc/lsb-release has a number of fields that look useful. However, before you try to use any of the fields in CrOS code, please consult the ChromiumOS Configuration document.

For example, you must not use CHROMEOS_RELEASE_BOARD from this file. That config document explains in more detail.

Format

Fundamentally, the file is a simple key-value store.

Files that don't follow these rules are malformed and not supported. Their usage/behavior is undefined and must not be relied upon.

• The keys/values are delimited by =.

• Line-based comments start with #.

• Inline comments are not supported.

• Blank lines are trimmed (including whitespace-only lines).

• Whitespace around the key is trimmed.

• Keys should be restricted to [A-Z0-9_].

• Duplicate keys are not supported.

• Leading & trailing whitespace around the value is trimmed.

• Whitespace in the value is permitted and retained.

• Quotes are not treated specially or removed and should be avoided.

• Values may not be line-wrapped or otherwise have newlines embedded.

• All other characters are permitted in the value.

Example Files

Here is an example /etc/lsb-release file.

# Normal line.
SOME_KEY=value
# Key and value with leading/trailing whitespace.
  WS_KEY  =    value
# Value with whitespace in the middle.
WS_VALUE = v a l u e
# Value with quotes don't get removed.
DOUBLE_QUOTES = "double"
SINGLE_QUOTES = 'sin gle'
RANDOM_QUOTES = '"

This is the JSON if that file was parsed and exported as such.

{
  "SOME_KEY": "value",
  "WS_KEY": "value",
  "WS_VALUE": "v a l u e",
  "DOUBLE_QUOTES": "\"double\"",
  "SINGLE_QUOTES": "'sin gle'",
  "RANDOM_QUOTES": "'\""
}

Coding Samples

If you want to access fields in this file, please do not parse it yourself.

C++

The SysInfo class is provided by libchrome in base/sys_info.h. See the methods that start with the GetLsb prefix.

#include <base/sys_info.h>
...
  std::string value;
  if (!base::SysInfo::GetLsbReleaseValue("CHROMEOS_RELEASE_TRACK", &value)) {
    LOG(ERROR) << "Could not load field from lsb-release";
    return false;
  }

  // Do something with |value| now.
...

Python

You can use ConfigParser.RawConfigParser to load /etc/lsb-release, but it takes a bit of effort due to missing section header. It also handles quoting and newlines differently.

The snippet below should handle all the edge cases.

def Load(path='/etc/lsb-release'):
    lines = [x.strip() for x in open(path).readlines()]
    return dict(map(lambda x: x.strip(), line.partition('=')[::2])
                for line in lines if line and not line.startswith('#'))

Shell

If you're writing shell code, you shouldn't be accessing this file. Please rewrite your code in a better language.

You absolutely must not source the file directly from shell code. e.g. Running . /etc/lsb-release is not guaranteed to ever work.

lsbval() {
  local key="$1"
  local lsbfile="${2:-/etc/lsb-release}"

  if ! echo "${key}" | grep -Eq '^[a-zA-Z0-9_]+$'; then
    return 1
  fi

  sed -E -n -e \
    "/^[[:space:]]*${key}[[:space:]]*=/{
      s:^[^=]+=[[:space:]]*::
      s:[[:space:]]+$::
      p
    }" "${lsbfile}"
}