get_ppid_of: New module.

* lib/get_ppid_of.h: New file.
* lib/get_ppid_of.c: New file.
* modules/get_ppid_of: New file.

4 files changed, 408 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 7f0fc1c37e..642f3da1cd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2019-08-14  Bruno Haible  <bruno@clisp.org>
+
+	get_ppid_of: New module.
+	* lib/get_ppid_of.h: New file.
+	* lib/get_ppid_of.c: New file.
+	* modules/get_ppid_of: New file.
+
 2019-08-13  Bruno Haible  <bruno@clisp.org>
 
 	libtextstyle-optional tests: Support the NO_COLOR environment variable.
diff --git a/lib/get_ppid_of.c b/lib/get_ppid_of.c
new file mode 100644
index 0000000000..01c442cbf1
--- /dev/null
+++ b/lib/get_ppid_of.c
@@ -0,0 +1,341 @@
+/* Determine the parent process of a given process.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2019.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "get_ppid_of.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#if defined __linux__ || defined __ANDROID__ || (defined __FreeBSD_kernel__ && !defined __FreeBSD__) || defined __GNU__ || defined __FreeBSD__ || defined __NetBSD__ || defined __minix || defined __sun /* Linux, GNU/kFreeBSD, GNU/Hurd, FreeBSD, NetBSD, Minix, Solaris */
+# include <fcntl.h>
+# include <unistd.h>
+#endif
+
+#if defined __OpenBSD__                                     /* OpenBSD */
+# include <sys/sysctl.h> /* sysctl, struct kinfo_proc */
+#endif
+
+#if defined __APPLE__ && defined __MACH__                   /* Mac OS X */
+# include <libproc.h>
+#endif
+
+#if defined _AIX                                            /* AIX */
+# include <procinfo.h>
+#endif
+
+#if defined __hpux                                          /* HP-UX */
+# include <unistd.h>
+# include <sys/param.h>
+# include <sys/pstat.h>
+#endif
+
+#if defined __sgi                                           /* IRIX */
+# include <unistd.h>
+# include <fcntl.h>
+# include <sys/procfs.h>
+#endif
+
+#if defined __CYGWIN__                                      /* Cygwin */
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h> /* needed to get 'struct external_pinfo' defined */
+# include <sys/cygwin.h>
+#endif
+
+#if defined __BEOS__ || defined __HAIKU__                   /* BeOS, Haiku */
+# include <unistd.h>
+#endif
+
+pid_t
+get_ppid_of (pid_t pid)
+{
+#if defined __linux__ || defined __ANDROID__ || (defined __FreeBSD_kernel__ && !defined __FreeBSD__) || defined __GNU__ /* Linux, GNU/kFreeBSD, GNU/Hurd */
+/* GNU/kFreeBSD mounts /proc as linprocfs, which looks like a Linux /proc
+   file system.  */
+
+  /* Read the contents of /proc/<pid>/status into memory.  */
+  char filename[6 + 10 + 7 + 1];
+  int fd;
+
+  sprintf (filename, "/proc/%u/status", (unsigned int) pid);
+  fd = open (filename, O_RDONLY);
+  if (fd >= 0)
+    {
+      char buf[4096 + 1];
+      ssize_t nread = read (fd, buf, sizeof (buf) - 1);
+      close (fd);
+      if (nread >= 0)
+        {
+          char *bufend = buf + nread;
+          char *p;
+
+          /* NUL-terminate the buffer.  */
+          *bufend = '\0';
+
+          /* Search for a line that starts with "PPid:".  */
+          for (p = buf;;)
+            {
+              if (bufend - p >= 5 && memcmp (p, "PPid:", 5) == 0)
+                {
+                  unsigned int ppid = 0;
+                  if (sscanf (p + 5, "%u", &ppid) > 0)
+                    return ppid;
+                }
+              p = strchr (p, '\n');
+              if (p != NULL)
+                p++;
+              else
+                break;
+            }
+        }
+    }
+
+#endif
+
+#if defined __FreeBSD__ || defined __NetBSD__               /* FreeBSD, NetBSD */
+
+  /* Read the contents of /proc/<pid>/status into memory.  */
+  char filename[6 + 10 + 7 + 1];
+  int fd;
+
+  sprintf (filename, "/proc/%u/status", (unsigned int) pid);
+  fd = open (filename, O_RDONLY);
+  if (fd >= 0)
+    {
+      char buf[4096 + 1];
+      ssize_t nread = read (fd, buf, sizeof (buf) - 1);
+      close (fd);
+      if (nread >= 0)
+        {
+          char *p;
+
+          /* NUL-terminate the buffer.  */
+          buf[nread] = '\0';
+
+          /* Search for the third space-separated field.  */
+          p = strchr (buf, ' ');
+          if (p != NULL)
+            {
+              p = strchr (p + 1, ' ');
+              if (p != NULL)
+                {
+                  unsigned int ppid = 0;
+                  if (sscanf (p + 1, "%u", &ppid) > 0)
+                    return ppid;
+                }
+            }
+        }
+    }
+
+#endif
+
+#if defined __minix                                         /* Minix */
+
+  /* Read the contents of /proc/<pid>/psinfo into memory.  */
+  char filename[6 + 10 + 7 + 1];
+  int fd;
+
+  sprintf (filename, "/proc/%u/psinfo", (unsigned int) pid);
+  fd = open (filename, O_RDONLY);
+  if (fd >= 0)
+    {
+      char buf[4096 + 1];
+      ssize_t nread = read (fd, buf, sizeof (buf) - 1);
+      close (fd);
+      if (nread >= 0)
+        {
+          char *p;
+          int count;
+
+          /* NUL-terminate the buffer.  */
+          buf[nread] = '\0';
+
+          /* Search for the 16th space-separated field.  */
+          p = strchr (buf, ' ');
+          for (count = 1; p != NULL && count < 15; count++)
+            p = strchr (p + 1, ' ');
+          if (p != NULL)
+            {
+              unsigned int ppid = 0;
+              if (sscanf (p + 1, "%u", &ppid) > 0)
+                return ppid;
+            }
+        }
+    }
+
+#endif
+
+#if defined __sun                                           /* Solaris */
+
+  /* Read the contents of /proc/<pid>/psinfo into memory.
+     Alternatively, we could read the contents of /proc/<pid>/status into
+     memory.  But it contains a lot of information that we don't need.  */
+  char filename[6 + 10 + 7 + 1];
+  int fd;
+
+  sprintf (filename, "/proc/%u/psinfo", (unsigned int) pid);
+  fd = open (filename, O_RDONLY);
+  if (fd >= 0)
+    {
+      /* The contents is a 'struct psinfo'.  But since 'struct psinfo'
+         has a different size in a 32-bit and a 64-bit environment, we
+         avoid it.  Nevertheless, the size of this contents depends on
+         whether the process that reads it is 32-bit or 64-bit!  */
+      #if defined __LP64__
+      # define PSINFO_SIZE 416
+      #else
+      # define PSINFO_SIZE 336
+      #endif
+      union { char all[PSINFO_SIZE]; unsigned int header[11]; } buf;
+      ssize_t nread = read (fd, buf.all, sizeof (buf.all));
+      close (fd);
+      if (nread >= (ssize_t) sizeof (buf.header))
+        return buf.header[3];
+    }
+
+#endif
+
+#if defined __OpenBSD__                                     /* OpenBSD */
+
+  /* Documentation: https://man.openbsd.org/sysctl.2  */
+  int info_path[] =
+    { CTL_KERN, KERN_PROC, KERN_PROC_PID, pid, sizeof (struct kinfo_proc), 1 };
+  struct kinfo_proc info;
+  size_t len;
+
+  len = sizeof (info);
+  if (sysctl (info_path, 6, &info, &len, NULL, 0) >= 0 && len == sizeof (info))
+    return info.p_ppid;
+
+#endif
+
+#if defined __APPLE__ && defined __MACH__                   /* Mac OS X */
+
+# if defined PROC_PIDT_SHORTBSDINFO
+  struct proc_bsdshortinfo info;
+
+  if (proc_pidinfo (pid, PROC_PIDT_SHORTBSDINFO, 0, &info, sizeof (info))
+      == sizeof (info))
+    return info.pbsi_ppid;
+# else
+  /* Note: The second part of 'struct proc_bsdinfo' differs in size between
+     32-bit and 64-bit environments, and the kernel of Mac OS X 10.5 knows
+     only about the 32-bit 'struct proc_bsdinfo'.  Fortunately all the info
+     we need is in the first part, which is the same in 32-bit and 64-bit.  */
+  struct proc_bsdinfo info;
+
+  if (proc_pidinfo (pid, PROC_PIDTBSDINFO, 0, &info, 128) == 128)
+    return info.pbi_ppid;
+# endif
+
+#endif
+
+#if defined _AIX                                            /* AIX */
+
+  /* Reference: https://www.ibm.com/support/knowledgecenter/en/ssw_aix_61/com.ibm.aix.basetrf1/getprocs.htm
+  */
+  struct procentry64 procs;
+  if (getprocs64 (&procs, sizeof procs, NULL, 0, &pid, 1) > 0)
+    return procs.pi_ppid;
+
+#endif
+
+#if defined __hpux                                          /* HP-UX */
+
+  struct pst_status status;
+  if (pstat_getproc (&status, sizeof status, 0, pid) > 0)
+    return status.pst_ppid;
+  else
+    {
+# if !defined __LP64__
+      /* Support for 32-bit programs running in 64-bit HP-UX.
+         The documented way to do this is to use the same source code
+         as above, but in a compilation unit where '#define _PSTAT64 1'
+         is in effect.  I prefer a single compilation unit; the struct
+         size and the offsets are not going to change.  */
+      char status64[1216];
+      if (__pstat_getproc64 (status64, sizeof status64, 0, pid) > 0)
+        return *(unsigned long long *)(status64 + 24);
+# endif
+    }
+
+#endif
+
+#if defined __sgi                                           /* IRIX */
+
+  char filename[12 + 10 + 1];
+  int fd;
+
+  sprintf (filename, "/proc/pinfo/%u", pid);
+  fd = open (filename, O_RDONLY);
+  if (0 <= fd)
+    {
+      prpsinfo_t buf;
+      int ioctl_ok = 0 <= ioctl (fd, PIOCPSINFO, &buf);
+      close (fd);
+      if (ioctl_ok)
+        return buf.pr_ppid;
+    }
+
+#endif
+
+#if defined __CYGWIN__                                      /* Cygwin */
+
+  struct external_pinfo *info =
+    (struct external_pinfo *) cygwin_internal (CW_GETPINFO, pid);
+  if (info != NULL)
+    return info->ppid;
+
+#endif
+
+#if defined __BEOS__ || defined __HAIKU__                   /* BeOS, Haiku */
+
+  if (pid == getpid ())
+    return getppid ();
+
+#endif
+
+  return 0;
+}
+
+#ifdef TEST
+
+#include <stdlib.h>
+#include <unistd.h>
+
+/* Usage: ./a.out
+   or:    ./a.out PID
+ */
+int
+main (int argc, char *argv[])
+{
+  char *arg = argv[1];
+  pid_t pid = (arg != NULL ? atoi (arg) : getpid ());
+  pid_t parent = get_ppid_of (pid);
+  printf ("PID=%lu PPID=%lu\n", (unsigned long) pid, (unsigned long) parent);
+  return 0;
+}
+
+/*
+ * Local Variables:
+ * compile-command: "gcc -ggdb -DTEST -Wall -I.. get_ppid_of.c"
+ * End:
+ */
+
+#endif
diff --git a/lib/get_ppid_of.h b/lib/get_ppid_of.h
new file mode 100644
index 0000000000..c757dfb643
--- /dev/null
+++ b/lib/get_ppid_of.h
@@ -0,0 +1,35 @@
+/* Determine the parent process of a given process.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2019.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _GET_PPID_OF_H
+#define _GET_PPID_OF_H
+
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Returns the process id of the parent process of the given process,
+   or 0 if it cannot be determined.  */
+extern pid_t get_ppid_of (pid_t pid);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _GET_PPID_OF_H */
diff --git a/modules/get_ppid_of b/modules/get_ppid_of
new file mode 100644
index 0000000000..4f2cad1b2c
--- /dev/null
+++ b/modules/get_ppid_of
@@ -0,0 +1,25 @@
+Description:
+Determine the parent process of a given process.
+
+Files:
+lib/get_ppid_of.h
+lib/get_ppid_of.c
+
+Depends-on:
+extensions
+sys_types
+unistd
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += get_ppid_of.h get_ppid_of.c
+
+Include:
+"get_ppid_of.h"
+
+License:
+LGPL
+
+Maintainer:
+all