Re: How to detect whether a process is running, on Linux, in the manner of 'pidof'?

[Jeff Pohlmeyer <yetanothergeek@...>]

I don't think kill() is going to help you, it requires a PID
as its argument, if you knew the PID, you would be done.

Here are two examples using the information in /proc:
  pidof_cmd() compares the first argument /proc/{PID}/cmdline
  pidof_exe() compares the link referenced by /proc/{PID}/exe

Both return a table of all PIDs matching the search criteria.

Not heavily tested, probably not a one-size-fits-all solution, but maybe
good enough depending on your use case.

#!/usr/bin/env lua

local posix=require 'posix'
local glob = posix.glob

function pidof_cmd(cmd)
  local pids={}
  for _, p in pairs(glob('/proc/[0-9]*/cmdline', 0)) do
    local f=io.open(p)
    if f then
      local s=f:read('*a')
      if s and #s>0 then
        s=s:gsub('\0.*$','')
        if s==cmd then
          table.insert(pids,(p:gsub('^/proc/(%d+)/.*$', '%1')))
        end
      end
    end
  end
  return pids
end

function pidof_exe(exe)
 local pids={}
  for _, p in pairs(glob('/proc/[0-9]*/exe', 0)) do
    local s=posix.readlink(p)
    if s==exe then
      table.insert(pids,(p:gsub('^/proc/(%d+)/.*$', '%1')))
    end
  end
  return pids
end

local cmd=arg[1]
local pidlist=pidof_exe(cmd)
for i,pid in ipairs(pidlist) do
  print(pid)
end

 -- Jeff