pidof: reimplemented from scratch (replacing sysvinit pidof)

As the sysvinit becomes obsolete, some of the bundled tools
need to find a new home. The procps-ng project seems to be
the most suitable project for adopting the pidof tool.
This commit introduces a redesigned version of pidof
that satisfies the LSB requirements.
In corner cases the behaviour might differ from the former
one as the new version doesn't use any stat(2) calls.

1 files changed, 371 insertions, 0 deletions

diff --git a/pidof.c b/pidof.c
new file mode 100644
index 0000000..6cce24c
--- /dev/null
+++ b/pidof.c
@@ -0,0 +1,371 @@
+/*
+ * pidof.c - Utility for listing pids of running processes
+ *
+ * Copyright (C) 2013  Jaromir Capik <jcapik@redhat.com>
+ *
+ * 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 2
+ * 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+#include <stdio.h>
+#include <getopt.h>
+
+#include "c.h"
+#include "fileutils.h"
+#include "nls.h"
+#include "xalloc.h"
+#include "proc/readproc.h"
+#include "proc/sig.h"
+#include "proc/devname.h"
+#include "proc/sysinfo.h"
+#include "proc/version.h" /* procps_version */
+
+
+#define grow_size(x)	(x = x * 5 / 4 + 1024)
+#define safe_free(x)	if (x) { free(x); x=NULL; }
+
+
+struct el {
+	pid_t pid;
+};
+
+struct el *procs = NULL;
+static int proc_count = 0;
+
+struct el *omitted_procs = NULL;
+static int omit_count = 0;
+
+static char *program = NULL;
+
+/* switch flags */
+static int opt_single_shot    = 0;  /* -s */
+static int opt_scripts_too    = 0;  /* -x */
+static int opt_rootdir_check  = 0;  /* -c */
+
+static char *pidof_root = NULL;
+
+static int __attribute__ ((__noreturn__)) usage(int opt)
+{
+	int err = (opt == '?');
+	FILE *fp = err ? stderr : stdout;
+
+	fputs(USAGE_HEADER, fp);
+	fprintf(fp, _(" %s [options] [program [...]]\n"), program_invocation_short_name);
+	fputs(USAGE_OPTIONS, fp);
+	fputs(_(" -s, --single-shot         return one PID only\n"
+		" -c, --check-root          omit processes with different root\n"
+		" -x                        scripts too\n"
+		" -o, --omit-pid <PID,...>  omit processes with PID\n"), fp);
+	fputs(USAGE_SEPARATOR, fp);
+	fputs(USAGE_HELP, fp);
+	fputs(USAGE_VERSION, fp);
+	fprintf(fp, USAGE_MAN_TAIL("pidof(1)"));
+
+	exit(fp == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
+}
+
+
+static int is_omitted (pid_t pid)
+{
+	int i;
+
+	for (i = 0; i < omit_count; i++) {
+		if (pid == omitted_procs[i].pid) return 1;
+	}
+
+	return 0;
+}
+
+
+static char *get_basename (char *filename)
+{
+	char *pos;
+	char *result;
+
+	pos = result = filename;
+	while (*pos != '\0') {
+		if (*(pos++) == '/') result = pos;
+	}
+
+	return result;
+}
+
+
+static char *pid_link (pid_t pid, const char *base_name)
+{
+	char link [PROCPATHLEN];
+	char *result;
+	int path_alloc_size;
+	int len;
+
+	snprintf(link, sizeof(link), "/proc/%d/%s", pid, base_name);
+
+	len = path_alloc_size = 0;
+	result = NULL;
+	do {
+		if (len == path_alloc_size) {
+			grow_size (path_alloc_size);
+			result = (char *) xrealloc (result, path_alloc_size);
+		}
+
+		if ((len = readlink(link, result, path_alloc_size - 1)) < 0) {
+			len = 0;
+			break;
+		}
+
+	} while (len == path_alloc_size);
+
+	result[len] = '\0';
+
+	return result;
+}
+
+
+static void select_procs (void)
+{
+	PROCTAB *ptp;
+	proc_t task;
+	int match, root_check_ok;
+	static int size = 0;
+	char *cmd_arg0, *cmd_arg0base;
+	char *cmd_arg1, *cmd_arg1base;
+	char *pos;
+	char *program_base;
+	char *root_link;
+	char *exe_link;
+	char *exe_link_base;
+
+	/* get the input base name */
+	program_base = get_basename(program);
+
+	ptp = openproc (PROC_FILLCOM | PROC_FILLSTAT);
+
+	exe_link = root_link = NULL;
+	memset(&task, 0, sizeof (task));
+	while(readproc(ptp, &task)) {
+
+		if (opt_rootdir_check) {
+			/* get the /proc/<pid>/root symlink value */
+			root_link = pid_link(task.XXXID, "root");
+			match = !strcmp(pidof_root, root_link);
+			safe_free(root_link);
+
+			if (!match) {  /* root check failed */
+				memset (&task, 0, sizeof (task));
+				continue;
+			}
+		}
+
+		if (!is_omitted(task.XXXID) && task.cmdline) {
+
+			cmd_arg0 = *task.cmdline;
+
+			/* processes starting with '-' are login shells */
+			if (*cmd_arg0 == '-') {
+				cmd_arg0++;
+			}
+
+			/* get the argv0 base name */
+			cmd_arg0base = get_basename(cmd_arg0);
+
+			/* get the /proc/<pid>/exe symlink value */
+			exe_link = pid_link(task.XXXID, "exe");
+
+			/* get the exe_link base name */
+			exe_link_base = get_basename(exe_link);
+
+			match = 0;
+
+			if (!strcmp(program, cmd_arg0base) ||
+			    !strcmp(program_base, cmd_arg0) ||
+			    !strcmp(program, cmd_arg0) ||
+
+			    !strcmp(program, exe_link_base) ||
+			    !strcmp(program, exe_link))
+			{
+				match = 1;
+
+			} else if (opt_scripts_too && *(task.cmdline+1)) {
+
+				pos = cmd_arg1base = cmd_arg1 = *(task.cmdline+1);
+
+				/* get the arg1 base name */
+				while (*pos != '\0') {
+					if (*(pos++) == '/') cmd_arg1base = pos;
+				}
+
+				/* if script, then task.cmd = argv1, otherwise task.cmd = argv0 */
+				if (task.cmd &&
+				    !strncmp(task.cmd, cmd_arg1base, strlen(task.cmd)) &&
+				    (!strcmp(program, cmd_arg1base) ||
+				    !strcmp(program_base, cmd_arg1) ||
+				    !strcmp(program, cmd_arg1)))
+				{
+					match = 1;
+				}
+			}
+
+			safe_free(exe_link);
+
+			if (match) {
+				if (proc_count == size) {
+					grow_size(size);
+					procs = xrealloc(procs, size * (sizeof *procs));
+				}
+				if (procs) {
+					procs[proc_count++].pid = task.XXXID;
+				} else {
+					xerrx(EXIT_FAILURE, _("internal error"));
+				}
+			}
+
+		}
+
+		memset (&task, 0, sizeof (task));
+	}
+
+	closeproc (ptp);
+}
+
+
+static void add_to_omit_list (char *input_arg)
+{
+	static int omit_size = 0;
+
+	char *omit_str;
+	char *endptr;
+
+	pid_t omit_pid;
+
+	omit_str = NULL;
+	omit_str = strtok(input_arg, ",");
+	while (omit_str) {
+
+		omit_pid = strtoul(omit_str, &endptr, 10);
+
+		if (*endptr == '\0') {
+			if (omit_count == omit_size) {
+				grow_size(omit_size);
+				omitted_procs = xrealloc(omitted_procs, omit_size * sizeof(*omitted_procs));
+			}
+			if (omitted_procs) {
+				omitted_procs[omit_count++].pid = omit_pid;
+			} else {
+				xerrx(EXIT_FAILURE, _("internal error"));
+			}
+		} else {
+			xwarnx(_("illegal omit pid value (%s)!\n"), omit_str);
+		}
+
+		omit_str = strtok(NULL, ",");
+	}
+}
+
+
+
+int main (int argc, char **argv)
+{
+	int opt;
+	signed int i;
+	int found = 0;
+	int first_pid = 1;
+
+	const char *opts = "scnxmo:?Vh";
+
+	static const struct option longopts[] = {
+		{"single-shot", no_argument, NULL, 's'},
+		{"omit-pid", required_argument, NULL, 'o'},
+		{"help", no_argument, NULL, 'h'},
+		{"version", no_argument, NULL, 'V'},
+		{NULL, 0, NULL, 0}
+	};
+
+#ifdef HAVE_PROGRAM_INVOCATION_NAME
+	program_invocation_name = program_invocation_short_name;
+#endif
+	setlocale (LC_ALL, "");
+	bindtextdomain (PACKAGE, LOCALEDIR);
+	textdomain (PACKAGE);
+	atexit (close_stdout);
+
+	/* process command-line options */
+	while ((opt = getopt_long (argc, argv, opts, longopts, NULL)) != -1) {
+		switch (opt) {
+		case 's':
+			opt_single_shot = 1;
+			break;
+		case 'o':
+			add_to_omit_list (optarg);
+			break;
+		case 'x':
+			opt_scripts_too = 1;
+			break;
+		case 'c':
+			if (geteuid() == 0) {
+				opt_rootdir_check = 1;
+				pidof_root = pid_link(getpid(), "root");
+			}
+			break;
+		case 'V':
+			printf (PROCPS_NG_VERSION);
+			exit (EXIT_SUCCESS);
+		case 'h':
+		case '?':
+			usage (opt);
+			break;
+		/* compatibility-only switches */
+		case 'n': /* avoiding stat(2) on NFS volumes doesn't make any sense anymore ... */
+			  /* ... as this reworked solution does not use stat(2) at all */
+		case 'm': /* omitting relatives with argv[0] & argv[1] matching the argv[0] & argv[1] ...*/
+			  /* ... of explicitly omitted PIDs is too 'expensive' and as we don't know */
+			  /* ... wheter it is still needed, we won't re-implement it unless ... */
+			  /* ... somebody gives us a good reason to do so :) */
+			break;
+		}
+	}
+
+	/* main loop */
+	while (argc - optind) {		/* for each program */
+
+		program = argv[optind++];
+
+		select_procs();	/* get the list of matching processes */
+
+		if (proc_count) {
+
+			found = 1;
+			for (i = proc_count - 1; i >= 0; i--) {	/* and display their PIDs */
+				if (first_pid) {
+					first_pid = 0;
+					printf ("%ld", procs[i].pid);
+				} else {
+					printf (" %ld", procs[i].pid);
+				}
+				if (opt_single_shot) break;
+			}
+
+			proc_count = 0;
+		}
+	}
+
+	/* final line feed */
+	if (found) printf("\n");
+
+	/* some cleaning */
+	safe_free(procs);
+	safe_free(omitted_procs);
+	safe_free(pidof_root);
+
+	return !found;
+}