How to get arguments of NSRunningApplication? - swift

Question

How do I get the list of arguments using during launch for a NSRunningApplication, similar to the ones I see when I run ps aux:
let workspace = NSWorkspace.shared
let applications = workspace.runningApplications
for application in applications {
// how do I get arguments that were used during application launch?
}

Answer 1

The "ps" tool uses sysctl() with KERN_PROCARGS2 to get the arguments of a running process. The following is an attempt to translate the code from adv_cmds-153/ps/print.c to Swift. That file also contains a documentation of the memory layout of the raw argument space and explains how to locate the string arguments in that memory.
func processArguments(pid: pid_t) -> [String]? {
// Determine space for arguments:
var name : [CInt] = [ CTL_KERN, KERN_PROCARGS2, pid ]
var length: size_t = 0
if sysctl(&name, CUnsignedInt(name.count), nil, &length, nil, 0) == -1 {
return nil
}
// Get raw arguments:
var buffer = [CChar](repeating: 0, count: length)
if sysctl(&name, CUnsignedInt(name.count), &buffer, &length, nil, 0) == -1 {
return nil
}
// There should be at least the space for the argument count:
var argc : CInt = 0
if length < MemoryLayout.size(ofValue: argc) {
return nil
}
var argv: [String] = []
buffer.withUnsafeBufferPointer { bp in
// Get argc:
memcpy(&argc, bp.baseAddress, MemoryLayout.size(ofValue: argc))
var pos = MemoryLayout.size(ofValue: argc)
// Skip the saved exec_path.
while pos < bp.count && bp[pos] != 0 {
pos += 1
}
if pos == bp.count {
return
}
// Skip trailing '\0' characters.
while pos < bp.count && bp[pos] == 0 {
pos += 1
}
if pos == bp.count {
return
}
// Iterate through the '\0'-terminated strings.
for _ in 0..<argc {
let start = bp.baseAddress! + pos
while pos < bp.count && bp[pos] != 0 {
pos += 1
}
if pos == bp.count {
return
}
argv.append(String(cString: start))
pos += 1
}
}
return argv.count == argc ? argv : nil
}
There is only a simple error handling: if anything goes wrong, the function returns nil.
For an instance of NSRunningApplication you can then call
processArguments(pid: application.processIdentifier)