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;
+}

3 files changed, 55 insertions, 13 deletions

diff --git a/src/nvim/os/fileio.c b/src/nvim/os/fileio.c
index d294f9139b..a95adc86b6 100644
--- a/src/nvim/os/fileio.c
+++ b/src/nvim/os/fileio.c
@@ -4,7 +4,7 @@
 /// @file fileio.c
 ///
 /// Buffered reading/writing to a file. Unlike fileio.c this is not dealing with
-/// Neovim stuctures for buffer, with autocommands, etc: just fopen/fread/fwrite
+/// Nvim stuctures for buffer, with autocommands, etc: just fopen/fread/fwrite
 /// replacement.
 
 #include <assert.h>
@@ -43,7 +43,7 @@
 /// @param[in]  mode  Permissions for the newly created file (ignored if flags
 ///                   does not have kFileCreate\*).
 ///
-/// @return Error code (@see os_strerror()) or 0.
+/// @return Error code, or 0 on success. @see os_strerror()
 int file_open(FileDescriptor *const ret_fp, const char *const fname,
               const int flags, const int mode)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
@@ -115,8 +115,7 @@ int file_open_fd(FileDescriptor *const ret_fp, const int fd, const bool wr)
 
 /// Like file_open(), but allocate and return ret_fp
 ///
-/// @param[out]  error  Error code, @see os_strerror(). Is set to zero on
-///                     success.
+/// @param[out]  error  Error code, or 0 on success. @see os_strerror()
 /// @param[in]  fname  File name to open.
 /// @param[in]  flags  Flags, @see FileOpenFlags.
 /// @param[in]  mode  Permissions for the newly created file (ignored if flags
@@ -137,8 +136,7 @@ FileDescriptor *file_open_new(int *const error, const char *const fname,
 
 /// Like file_open_fd(), but allocate and return ret_fp
 ///
-/// @param[out]  error  Error code, @see os_strerror(). Is set to zero on
-///                     success.
+/// @param[out]  error  Error code, or 0 on success. @see os_strerror()
 /// @param[in]  fd  File descriptor to wrap.
 /// @param[in]  wr  True if fd is opened for writing only, false if it is read
 ///                 only.
diff --git a/src/nvim/os/process.c b/src/nvim/os/process.c
index 09769925ac..e23ba8a4ee 100644
--- a/src/nvim/os/process.c
+++ b/src/nvim/os/process.c
@@ -1,6 +1,11 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
+/// OS process functions
+///
+/// psutil is a good reference for cross-platform syscall voodoo:
+/// https://github.com/giampaolo/psutil/tree/master/psutil/arch
+
 #include <uv.h>  // for HANDLE (win32)
 
 #ifdef WIN32
@@ -18,10 +23,12 @@
 # include <pwd.h>
 #endif
 
+#include "nvim/globals.h"
 #include "nvim/log.h"
 #include "nvim/os/process.h"
 #include "nvim/os/os.h"
 #include "nvim/os/os_defs.h"
+#include "nvim/api/private/helpers.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "os/process.c.generated.h"
@@ -104,11 +111,6 @@ bool os_proc_tree_kill(int pid, int sig)
 /// @return 0 on success, 1 if process not found, 2 on other error.
 int os_proc_children(int ppid, int **proc_list, size_t *proc_count)
 {
-  //
-  // psutil is a good reference for cross-platform syscall voodoo:
-  // https://github.com/giampaolo/psutil/tree/master/psutil/arch
-  //
-
   if (ppid < 0) {
     return 2;
   }
@@ -122,13 +124,13 @@ int os_proc_children(int ppid, int **proc_list, size_t *proc_count)
 
   // Snapshot of all processes.
   HANDLE h = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
-  if(h == INVALID_HANDLE_VALUE) {
+  if (h == INVALID_HANDLE_VALUE) {
     return 2;
   }
 
   pe.dwSize = sizeof(PROCESSENTRY32);
   // Get root process.
-  if(!Process32First(h, &pe)) {
+  if (!Process32First(h, &pe)) {
     CloseHandle(h);
     return 2;
   }
@@ -208,3 +210,44 @@ int os_proc_children(int ppid, int **proc_list, size_t *proc_count)
   return 0;
 }
 
+#ifdef WIN32
+/// 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;
+  PROCESSENTRY32 pe;
+
+  // Snapshot of all processes.  This is used instead of:
+  //    OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, …)
+  // to avoid ERROR_PARTIAL_COPY.  https://stackoverflow.com/a/29942376
+  HANDLE h = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
+  if (h == INVALID_HANDLE_VALUE) {
+    return pinfo;  // Return empty.
+  }
+
+  pe.dwSize = sizeof(PROCESSENTRY32);
+  // Get root process.
+  if (!Process32First(h, &pe)) {
+    CloseHandle(h);
+    return pinfo;  // Return empty.
+  }
+  // Find the process.
+  do {
+    if (pe.th32ProcessID == (DWORD)pid) {
+      break;
+    }
+  } while (Process32Next(h, &pe));
+  CloseHandle(h);
+
+  if (pe.th32ProcessID == (DWORD)pid) {
+    PUT(pinfo, "pid", INTEGER_OBJ(pid));
+    PUT(pinfo, "ppid", INTEGER_OBJ((int)pe.th32ParentProcessID));
+    PUT(pinfo, "name", STRING_OBJ(cstr_to_string(pe.szExeFile)));
+  }
+
+  return pinfo;
+}
+#endif
diff --git a/src/nvim/os/process.h b/src/nvim/os/process.h
index 9a83942169..1722d56bd3 100644
--- a/src/nvim/os/process.h
+++ b/src/nvim/os/process.h
@@ -2,6 +2,7 @@
 #define NVIM_OS_PROCESS_H
 
 #include <stddef.h>
+#include "nvim/api/private/defs.h"
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "os/process.h.generated.h"