API: nvim_get_proc()

TODO: "exepath" field (win32: QueryFullProcessImageName())

On unix-likes `ps` is used because the platform-specific APIs are
a nightmare.  For reference, below is a (incomplete) attempt:

diff --git a/src/nvim/os/process.c b/src/nvim/os/process.c
index 09769925aca5..99afbbf290c1 100644
--- a/src/nvim/os/process.c
+++ b/src/nvim/os/process.c
@@ -208,3 +210,60 @@ int os_proc_children(int ppid, int **proc_list, size_t *proc_count)
   return 0;
 }

+/// Gets various properties of the process identified by `pid`.
+///
+/// @param pid Process to inspect.
+/// @return Map of process properties, empty on error.
+Dictionary os_proc_info(int pid)
+{
+  Dictionary pinfo = ARRAY_DICT_INIT;
+#ifdef WIN32
+
+#elif defined(__APPLE__)
+  char buf[PROC_PIDPATHINFO_MAXSIZE];
+  if (proc_pidpath(pid, buf, sizeof(buf))) {
+    name = getName(buf);
+    PUT(pinfo, "exepath", STRING_OBJ(cstr_to_string(buf)));
+    return name;
+  } else {
+    ILOG("proc_pidpath() failed for pid: %d", pid);
+  }
+#elif defined(BSD)
+# if defined(__FreeBSD__)
+#  define KP_COMM(o) o.ki_comm
+# else
+#  define KP_COMM(o) o.p_comm
+# endif
+  struct kinfo_proc *proc = kinfo_getproc(pid);
+  if (proc) {
+    PUT(pinfo, "name", cstr_to_string(KP_COMM(proc)));
+    xfree(proc);
+  } else {
+    ILOG("kinfo_getproc() failed for pid: %d", pid);
+  }
+
+#elif defined(__linux__)
+  char fname[256] = { 0 };
+  char buf[MAXPATHL];
+  snprintf(fname, sizeof(fname), "/proc/%d/comm", pid);
+  FILE *fp = fopen(fname, "r");
+  // FileDescriptor *f = file_open_new(&error, fname, kFileReadOnly, 0);
+  // ptrdiff_t file_read(FileDescriptor *const fp, char *const ret_buf,
+  //                     const size_t size)
+  if (fp == NULL) {
+    ILOG("fopen() of /proc/%d/comm failed", pid);
+  } else {
+    size_t n = fread(buf, sizeof(char), sizeof(buf) - 1, fp);
+    if (n == 0) {
+      WLOG("fread() of /proc/%d/comm failed", pid);
+    } else {
+      size_t end = MIN(sizeof(buf) - 1, n);
+      end = (end > 0 && buf[end - 1] == '\n') ? end - 1 : end;
+      buf[end] = '\0';
+      PUT(pinfo, "name", STRING_OBJ(cstr_to_string(buf)));
+    }
+  }
+  fclose(fp);
+#endif
+  return pinfo;
+}

1 files changed, 31 insertions, 3 deletions

diff --git a/test/functional/api/proc_spec.lua b/test/functional/api/proc_spec.lua
index eee54f9465..d99c26b6c2 100644
--- a/test/functional/api/proc_spec.lua
+++ b/test/functional/api/proc_spec.lua
@@ -1,10 +1,14 @@
 local helpers = require('test.functional.helpers')(after_each)
 
-local clear, eq = helpers.clear, helpers.eq
+local clear = helpers.clear
+local eq = helpers.eq
 local funcs = helpers.funcs
+local iswin = helpers.iswin
 local nvim_argv = helpers.nvim_argv
+local ok = helpers.ok
 local request = helpers.request
 local retry = helpers.retry
+local NIL = helpers.NIL
 
 describe('api', function()
   before_each(clear)
@@ -43,11 +47,35 @@ describe('api', function()
       eq(false, status)
       eq("Invalid pid: 0", string.match(rv, "Invalid.*"))
 
-      -- Assume PID 99999999 does not exist.
-      status, rv = pcall(request, "nvim_get_proc_children", 99999999)
+      -- Assume PID 99999 does not exist.
+      status, rv = pcall(request, "nvim_get_proc_children", 99999)
       eq(true, status)
       eq({}, rv)
     end)
   end)
 
+  describe('nvim_get_proc', function()
+    it('returns process info', function()
+      local pid = funcs.getpid()
+      local pinfo = request('nvim_get_proc', pid)
+      eq((iswin() and 'nvim.exe' or 'nvim'), pinfo.name)
+      ok(pinfo.pid == pid)
+      ok(type(pinfo.ppid) == 'number' and pinfo.ppid ~= pid)
+    end)
+
+    it('validates input', function()
+      local status, rv = pcall(request, "nvim_get_proc", -1)
+      eq(false, status)
+      eq("Invalid pid: -1", string.match(rv, "Invalid.*"))
+
+      status, rv = pcall(request, "nvim_get_proc", 0)
+      eq(false, status)
+      eq("Invalid pid: 0", string.match(rv, "Invalid.*"))
+
+      -- Assume PID 99999 does not exist.
+      status, rv = pcall(request, "nvim_get_proc", 99999)
+      eq(true, status)
+      eq(NIL, rv)
+    end)
+  end)
 end)