msys.os.statvfs_read
Name
msys.os.statvfs_read — Request a snapshot of the stream
Synopsis
require('msys.os');
msys.os.statvfs_read(path);
Description
This function provides a "stream" for statvfs updates. This guarantees minimal blocking and it is safe to call this functions from the context of any thread. The developer first requests an ec_statvfs_record_t object by calling msys.os.statvfs_subscribe.
Find below an example of requesting a statvfs snapshot stream on /tmp updated at least every 10 seconds:
r = msys.os.statvfs_subscribe("/tmp", 10);
msys.os.statvfs_subscribe is guaranteed to fail only due to failed memory allocation. If interval is 0, then an implementation-default value is used for the interval length. After a user has subscribed to a snapshot stream associated with a path, they may use msys.os.statvfs_read to read the latest available snapshot. If several subscriptions exist for a given path, the smallest requested interval will be used. If a user requests a smaller interval than the default, then the interval update occurs on the previous interval edge.
Find below an example of requesting latest snapshot for /tmp and then printing total available kilobytes:
st, e = msys.os.statvfs_read(cache[path]); if (st == nil) then print (e); else print (st["kilobytes_total"]); end
If st is nil then e will contain the error message associated with the failure. st is userdata of type ec_statvfs_t and contains values for the following keys:
-
version
-
kilobytes_available
-
kilobytes_total
-
objects_available
-
objects_total
The following script example provides "subscribe" and "read" commands to ec_console.
require("msys.core");
require("msys.os");
local cache = {};
local function subscribe(cc)
-- Check the number of parameters
if cc.argc < 2 then
print ("You must pass a parameter to this command");
return;
end
local path = cc.argv[1];
if cache[path] == nil then
cache[path] = msys.os.statvfs_subscribe(path, 5);
if (cache[path] == nil) then
print ("Memory exhausted.");
else
print ("Created subscription for " .. path);
end
end
end
local function read(cc)
-- Check the number of parameters
if cc.argc < 2 then
print("You must pass a parameter to this command");
return;
end
local path = cc.argv[1];
local st = nil;
if cache[path] == nil then
print ("ERROR: No subscription found.");
end
st, e = msys.os.statvfs_read(cache[path]);
if (st == nil) then
print (e);
else
print ("Version : " .. st["version"]);
print ("Available kB : " .. st["kilobytes_available"]);
print ("Total kB : " .. st["kilobytes_total"]);
print ("Available objects: " .. st["objects_available"]);
print ("Total objects : " .. st["objects_total"]);
end
return st;
end
msys.registerControl("subscribe", subscribe)
msys.registerControl("read", read)
Enable this function with the statement require('msys.os');.
Command Construct Userdata
The function that performs the registered action, in the examples above, accepts as a parameter command_construct userdata. cc.argc returns the number of arguments supplied by the console command, with the first argument being the command name. cc.argv[0] is the command name and cc.argv[1] is the command option. For more sophisticated argument parsing use require("msys.getopt");. For more information examine the getopt.lua file found in the /opt/msys/ecelerity/libexec/scriptlets/msys directory.