/* run-parts: run a bunch of scripts in a directory
 *
 * Debian run-parts program
 * Copyright (C) 1996 Jeff Noxon <jeff@router.patch.net>,
 * Copyright (C) 1996-1999 Guy Maor <maor@debian.org>
 * Copyright (C) 2002-2020 Clint Adams <clint@debian.org>
 *
 * This is free software; see the GNU General Public License version 2
 * or later for copying conditions.  There is NO warranty.
 *
 * Based on run-parts.pl version 0.2, Copyright (C) 1994 Ian Jackson.
 *
 */
#define _GNU_SOURCE

#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <dirent.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#ifdef HAVE_GETOPT_H
#include <getopt.h>
#endif /* HAVE_GETOPT_H */
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <signal.h>
#include <sys/time.h>
#include <regex.h>
#include <inttypes.h>

#define RUNPARTS_NORMAL 0
#define RUNPARTS_ERE 1
#define RUNPARTS_LSBSYSINIT 100

int test_mode = 0;
int list_mode = 0;
int verbose_mode = 0;
int debug_mode = 0;
int report_mode = 0;
int reverse_mode = 0;
int exitstatus = 0;
int regex_mode = 0;
int exit_on_error_mode = 0;
int new_session_mode = 0;
int stdin_mode = 0;
int stdin_fd = -1; // initialized in run_parts() if {stdin_mode} != 0


int argcount = 0, argsize = 0;
char **args = 0;

char *custom_ere;
regex_t hierre, tradre, excsre, classicalre, customre;

char *run_before, *run_after;

static void catch_signals();
static void restore_signals();

static char* regex_get_error(int errcode, regex_t *compiled);
static void  regex_compile_pattern(void);
static void  regex_clean(void);

__attribute__((format (printf, 1, 2)))
void error(const char *format, ...)
{
  va_list ap;

  fprintf(stderr, "run-parts: ");

  va_start(ap, format);
  vfprintf(stderr, format, ap);
  va_end(ap);

  fprintf(stderr, "\n");
}


void version()
{
  printf( "Debian run-parts program, version " PACKAGE_VERSION
	  "\nCopyright (C) 1994 Ian Jackson, Copyright (C) 1996 Jeff Noxon.\n"
	  "Copyright (C) 1996,1997,1998,1999 Guy Maor\n"
	  "Copyright (C) 2002-2020 Clint Adams\n"
	  "This is free software; see the GNU General Public License version 2\n"
	  "or later for copying conditions.  There is NO warranty.\n");
  exit(0);
}


void usage()
{
  printf("Usage: run-parts [OPTION]... DIRECTORY [DIRECTORY ...]\n"
	  "      --test          print script names which would run, but don't run them.\n"
	  "      --list          print names of all valid files (can not be used with\n"
	  "                      --test)\n"
	  "  -v, --verbose       print script names before running them.\n"
	  "  -d, --debug         print script names while checking them.\n"
	  "      --report        print script names if they produce output.\n"
	  "      --reverse       reverse execution order of scripts.\n"
	  "      --exit-on-error exit as soon as a script returns with a non-zero exit\n"
	  "                      code.\n"
	  "      --stdin         multiplex stdin to scripts being run, using temporary file\n"
	  "      --lsbsysinit    validate filenames based on LSB sysinit specs.\n"
	  "      --new-session   run each script in a separate process session\n"
	  "      --regex=PATTERN validate filenames based on POSIX ERE pattern PATTERN.\n"
	  "  -u, --umask=UMASK   sets umask to UMASK (octal), default is 022.\n"
	  "  -a, --arg=ARGUMENT  pass ARGUMENT to scripts, use once for each argument.\n"
	  "  -A, --after=PROG    run PROG after each script runs.\n"
	  "  -B, --before=PROG   run PROG before running each script.\n"
	  "  -V, --version       output version information and exit.\n"
	  "  -h, --help          display this help and exit.\n");
  exit(0);
}


/* The octal conversion in libc is not foolproof; it will take the 8 and 9
 * digits under some circumstances.  We'll just have to live with it.
 */
void set_umask()
{
  unsigned int mask, result;

  result = sscanf(optarg, "%o", &mask);
  if ((result != 1) || (mask > 07777) || (mask < 0)) {
    error("bad umask value");
    exit(1);
  }

  umask(mask);
}

/* Add an argument to the commands that we will call.  Called once for
   every argument. */
void add_argument(char *newarg)
{
  if (argcount + 1 >= argsize) {
    argsize = argsize ? argsize * 2 : 4;
    args = realloc(args, argsize * (sizeof(char *)));
    if (!args) {
      error("failed to reallocate memory for arguments: %s", strerror(errno));
      exit(1);
    }
  }
  args[argcount++] = newarg;
  args[argcount] = 0;
}

/* True or false? Is this a valid filename? */
int valid_name(const struct dirent *d)
{
    char         *s;
    unsigned int  retval;

    s = (char *)&(d->d_name);

    if (regex_mode == RUNPARTS_ERE) {
        retval = !regexec(&customre, s, 0, NULL, 0);
	if (debug_mode)
	    fprintf(stderr, "\"%s\": customre %s\n", s, retval ? "pass" : "fail");

    } else if (regex_mode == RUNPARTS_LSBSYSINIT) {

        if (!regexec(&hierre, s, 0, NULL, 0)) {
            retval = regexec(&excsre, s, 0, NULL, 0);
	    if (debug_mode)
		fprintf(stderr, "\"%s\": hierre pass, excsre %s\n", s, retval ? "pass" : "fail");

	} else {
            retval = !regexec(&tradre, s, 0, NULL, 0);
	    if (debug_mode)
		fprintf(stderr, "\"%s\": tradre %s\n", s, retval ? "pass" : "fail");

	}
    } else {
        retval = !regexec(&classicalre, s, 0, NULL, 0);
	if (debug_mode)
	    fprintf(stderr, "\"%s\": classicalre %s\n", s, retval ? "pass" : "fail");

    }

    return retval;
}

/* wait for call return */
static void wait_for_call(pid_t pid, char *progname, char **run_what)
{
  int result, rtc = 0, r;
  r = waitpid(pid, &result, 0);

  if (r == -1) {
    error("waitpid: %s", strerror(errno));
    exit(1);
  }

  if (WIFEXITED(result) && WEXITSTATUS(result)) {
    error("%s %s exited with return code %d", *run_what, progname,
      rtc = WEXITSTATUS(result));
  }
  else if (WIFSIGNALED(result)) {
    error("%s exited because of uncaught signal %d", *run_what,
      WTERMSIG(result));
    rtc = 1;
  }

  if (rtc)
    *run_what = NULL;
}

/* run run_before */
static void call_run_before(char *progname)
{
  pid_t pid = fork();
  if (pid < 0) {
    error("failed to fork: %s", strerror(errno));
    exit(1);
  }
  else if (!pid) {
    restore_signals();
    char *argv[3] = {run_before, progname, NULL};
    execvp(run_before, argv);
    error("failed to exec %s: %s", run_before, strerror(errno));
    exit(1);
  }

  wait_for_call(pid, progname, &run_before);
}

/* run run_after */
static void call_run_after(char *progname, uint64_t tot_wrote)
{
  pid_t pid = fork();
  if (pid < 0) {
    error("failed to fork: %s", strerror(errno));
    exit(1);
  }
  else if (!pid) {
    char wrote[32], status[32];
    restore_signals();
    snprintf(status, sizeof status, "%d", exitstatus);
    snprintf(wrote, sizeof wrote, "%" PRIu64, tot_wrote);
    char *argv[5] = {run_after, progname, status, wrote, NULL};
    execvp(run_after, argv);
    error("failed to exec %s: %s", run_after, strerror(errno));
    exit(1);
  }

  wait_for_call(pid, progname, &run_after);
}

/* Execute a file */
void run_part(char *progname)
{
  int result, waited;
  int pid, r;
  int pout[2], perr[2];
  uint64_t tot_wrote = 0;

  waited = 0;

  if (report_mode && (pipe(pout) || pipe(perr))) {
    error("pipe: %s", strerror(errno));
    exit(1);
  }

  if (run_before)
    call_run_before(progname);

  if ((pid = fork()) < 0) {
    error("failed to fork: %s", strerror(errno));
    exit(1);
  }
  else if (!pid) {
    restore_signals();
    if (new_session_mode)
      setsid();

    if (stdin_mode) {
      if (dup2(stdin_fd, STDIN_FILENO) == -1) {
        error("dup2: %s", strerror(errno));
        exit(1);
      }
      if (lseek(STDIN_FILENO, 0, SEEK_SET) == (off_t) -1) {
        error("run-parts: failed to rewind temporary file: %s\n", strerror(errno));
        exit(1);
      }
    }
    if (report_mode) {
      if (dup2(pout[1], STDOUT_FILENO) == -1 ||
	  dup2(perr[1], STDERR_FILENO) == -1) {
	error("dup2: %s", strerror(errno));
	exit(1);
      }
      close(pout[0]);
      close(perr[0]);
      close(pout[1]);
      close(perr[1]);
    }
    args[0] = progname;
    execv(progname, args);
    error("failed to exec %s: %s", progname, strerror(errno));
    exit(1);
  }

  if (report_mode) {
    fd_set set;
    sigset_t tempmask;
    struct timespec zero_timeout;
    struct timespec *the_timeout;
    int max, printflag;
    ssize_t c;
    char buf[4096];

    sigemptyset(&tempmask);
    sigprocmask(0, NULL, &tempmask);
    sigdelset(&tempmask, SIGCHLD);

    memset(&zero_timeout, 0, sizeof(zero_timeout));
    the_timeout = NULL;

    close(pout[1]);
    close(perr[1]);
    max = pout[0] > perr[0] ? pout[0] + 1 : perr[0] + 1;
    printflag = 0;

    while (pout[0] >= 0 || perr[0] >= 0) {
      if (!waited) {
        r = waitpid(pid, &result, WNOHANG);
        if (r == -1) {
          error("waitpid: %s", strerror(errno));
          exit(1);
        }
        if (r != 0 && (WIFEXITED(result) || WIFSIGNALED(result))) {
          /* If the process dies, set a zero timeout. Rarely, some processes
           * leak file descriptors (e.g., by starting a naughty daemon).
           * select() would wait forever since the pipes wouldn't close.
           * We loop, with a zero timeout, until there's no data left, then
           * give up. This shouldn't affect non-leaky processes. */
          waited = 1;
          the_timeout = &zero_timeout;
        }
      }

      FD_ZERO(&set);
      if (pout[0] >= 0)
        FD_SET(pout[0], &set);
      if (perr[0] >= 0)
        FD_SET(perr[0], &set);
      r = pselect(max, &set, 0, 0, the_timeout, &tempmask);

      if (r < 0) {
        if (errno == EINTR)
            continue;

        error("select: %s", strerror(errno));
        exit(1);
      }
      else if (r > 0) {
	/* If STDOUT or STDERR get closed / full, we still run to completion
	 * (and just ignore that we can't output process output any more).
	 * Perhaps we should instead kill the child process we are running
	 * if that happens.
	 * For now partial writes are not retried to complete - that can
	 * and should be done, but needs care to ensure that we don't hang
	 * if the fd doesn't accept more data ever - or we need to decide that
	 * waiting is the appropriate thing to do.
	 */
	int ignored;
	if (pout[0] >= 0 && FD_ISSET(pout[0], &set)) {
	  c = read(pout[0], buf, sizeof(buf));
	  if (c > 0) {
	    if (!printflag) {
	      printf("%s:\n", progname);
	      fflush(stdout);
	      printflag = 1;
	    }
	    tot_wrote += c;
	    ignored = write(STDOUT_FILENO, buf, c);
	  }
	  else if (c == 0) {
	    close(pout[0]);
	    pout[0] = -1;
	  }
	  else if (c < 0) {
	    close(pout[0]);
	    pout[0] = -1;
	    error("failed to read from stdout pipe: %s", strerror (errno));
	  }
	}
	if (perr[0] >= 0 && FD_ISSET(perr[0], &set)) {
	  c = read(perr[0], buf, sizeof(buf));
	  if (c > 0) {
	    if (!printflag) {
	      fprintf(stderr, "%s:\n", progname);
	      fflush(stderr);
	      printflag = 1;
	    }
	    tot_wrote += c;
	    ignored = write(STDERR_FILENO, buf, c);
	  }
	  else if (c == 0) {
	    close(perr[0]);
	    perr[0] = -1;
	  }
	  else if (c < 0) {
	    close(perr[0]);
	    perr[0] = -1;
	    error("failed to read from error pipe: %s", strerror (errno));
	  }
	}
      }
      else if (r == 0 && waited) {
        /* Zero timeout, no data left. */
        close(perr[0]);
        perr[0] = -1;
        close(pout[0]);
        pout[0] = -1;
      }
      else {
	/* assert(FALSE): select was called with infinite timeout, so
	   it either returns successfully or is interrupted */
      }				/*if */
    }				/*while */
  }

  if (!waited) {
    r = waitpid(pid, &result, 0);

    if (r == -1) {
		  error("waitpid: %s", strerror(errno));
			exit(1);
    }
  }

  if (WIFEXITED(result) && WEXITSTATUS(result)) {
    error("%s exited with return code %d", progname, WEXITSTATUS(result));
    exitstatus = WEXITSTATUS(result);
  }
  else if (WIFSIGNALED(result)) {
    error("%s exited because of uncaught signal %d", progname,
	  WTERMSIG(result));
    exitstatus = 1;
  }

  if (run_after)
    call_run_after(progname, tot_wrote);
}

static void handle_signal(int s)
{
    /* Do nothing */
}

/* Catch SIGCHLD with an empty function to interrupt select() */
static void catch_signals()
{
    struct sigaction act;
    sigset_t set;

    memset(&act, 0, sizeof(act));
    act.sa_handler = handle_signal;
    act.sa_flags = SA_NOCLDSTOP;
    sigaction(SIGCHLD, &act, NULL);

    sigemptyset(&set);
    sigaddset(&set, SIGCHLD);
    sigprocmask(SIG_BLOCK, &set, NULL);
}

/* Unblock signals before execing a child */
static void restore_signals()
{
    sigset_t set;
    sigemptyset(&set);
    sigaddset(&set, SIGCHLD);
    sigprocmask(SIG_UNBLOCK, &set, NULL);
}

#ifdef O_TMPFILE
static int open_tmpfile_rw(void)
{
	const char *tmpdir;

	tmpdir = getenv("TMPDIR");
	if (!tmpdir) {
		tmpdir = "/tmp";
	}

	return open(tmpdir, O_TMPFILE|O_RDWR|O_EXCL, S_IRUSR | S_IWUSR);
}
#else
static char tmpfile_path[] = "/tmp/run-parts.stdin.XXXXXX";
static void cleanup_tmpfile(void)
{
	unlink(tmpfile_path);
}

static int open_tmpfile_rw(void)
{
	int fd;

	fd = mkstemp(tmpfile_path);
	if (fd != -1) {
		atexit(&cleanup_tmpfile);
	}
	return fd;
}
#endif

/*
 * Copy stdin into temporary read-write file, and return file descriptor to it.
 */
static int copy_stdin(void)
{
  int fd;
  char buffer[4096];
  ssize_t bytes;

  fd = open_tmpfile_rw();

  do {
    ssize_t rest;

    bytes = rest = read(STDIN_FILENO, buffer, sizeof(buffer));
    if (bytes < 0) {
      error("run-parts: failed to read from stdin\n");
      close(fd);
      return -1;
    }

    while (rest > 0) {
      ssize_t written;

      written = write(fd, buffer, rest);
      if (written < 0) {
        error("run-parts: failed to write to temporary file\n");
        close(fd);
        return -1;
      }
      rest -= written;
    }
  } while (bytes > 0);

  return fd;
}

static int qsort_strcoll(const void *p1, const void *p2) {
  /* The actual arguments to this function are "pointers to
     pointers to char", but strcoll(3) arguments are "pointers
     to char", hence the following cast plus dereference. */
  return strcoll(*(const char **)p1, *(const char **)p2);
}

static int remove_dupes(char **list, int len) {
	if (len == 0) {
		return 0;
	}
	int j = 1;
	for (int i = 1; i < len; i++) {
		// compare each element with the one before
		if (strcmp(list[j-1], list[i]) == 0) {
			// found duplicate, free memory
			free(list[i]);
			continue;
		}
		// not a duplicate
		list[j] = list[i];
		j++;
	}
	return j;
}

/* Find the parts to run & call run_part() */
void run_parts(char **dirnames)
{
  struct stat st;

  /* 1st step: gather a list of all files in the given directories */

  char **basenames = NULL;
  int num_basenames = 0;
  for (int i = 0; dirnames[i] != NULL; i++) {
    DIR *dirfd = opendir(dirnames[i]);
    if (!dirfd) {
      continue;
    }
    struct dirent *dp;
    while ((dp = readdir(dirfd)) != NULL) {
      if (!strcmp(dp->d_name, ".") || !strcmp(dp->d_name, "..")) {
        continue;
      }
      if (!valid_name(dp)) {
        continue;
      }
      num_basenames++;
      if (!(basenames = realloc(basenames, num_basenames * sizeof(char *)))) {
        error("failed to reallocate memory for basenames: %s", strerror(errno));
        exit(1);
      }
      basenames[num_basenames - 1] = strdup(dp->d_name);
    }
  }

  if (num_basenames == 0) {
    // nothing to do
    return;
  }

  /* 2nd step: sort that list with alphasort */

  qsort(basenames, num_basenames, sizeof(char *), qsort_strcoll);

  /* 3rd step: make the sorted list only contain unique elements */

  num_basenames = remove_dupes(basenames, num_basenames);
  if (!(basenames = realloc(basenames, num_basenames * sizeof(char *)))) {
    error("failed to reallocate memory for basenames: %s", strerror(errno));
    exit(1);
  }
  if (debug_mode) {
    fprintf(stderr, "list of unique basenames:\n");
    for (int i = 0; i < num_basenames; i++) {
      fprintf(stderr, " - %s\n", basenames[i]);
    }
  }

  /* 4th step: for each of the basenames, loop over the given directories
   *           and store the full path of the first directory in which a
   *           file with that basename was found */
  char **full_paths = NULL;
  int num_full_paths = 0;
  char *tmp_full_path = NULL;
  int max_full_path_length = 0;
  for (int i = 0; i < num_basenames; i++) {
    // Try to find the filename in each of the given directories, first match
    // wins.
    size_t basename_length = strlen(basenames[i]);
    for (int j = 0; dirnames[j] != NULL; j++) {
      size_t dirname_length = strlen(dirnames[j]);
      // check if we need to increase the buffer for the temporary full path
      if (max_full_path_length < basename_length + dirname_length + 2) {
        max_full_path_length = basename_length + dirname_length + 2;
        if (!(tmp_full_path = realloc(tmp_full_path, max_full_path_length))) {
          error("failed to reallocate memory for path: %s", strerror(errno));
          exit(1);
        }
      }
      strcpy(tmp_full_path, dirnames[j]);
      strcpy(tmp_full_path + dirname_length, "/");
      strcpy(tmp_full_path + dirname_length + 1, basenames[i]);
      if (debug_mode)
        fprintf(stderr, "checking %s... ", tmp_full_path);
      int result = stat(tmp_full_path, &st);
      if (result < 0) {
        if (debug_mode)
          fprintf(stderr, "not found\n");
        // not found in this directory, keep searching
        continue;
      }
      // this path exists, so do not search further directories for matches
      num_full_paths++;
      if (!(full_paths = realloc(full_paths, num_full_paths * sizeof(char *)))) {
        error("failed to reallocate memory for full paths: %s", strerror(errno));
        exit(1);
      }
      full_paths[num_full_paths - 1] = strdup(tmp_full_path);
      if (debug_mode)
        fprintf(stderr, "found\n");
      break;
    }
  }

  if (stdin_mode) {
    stdin_fd = copy_stdin();
    if (stdin_fd < 0) {
      error("run-parts: failed to copy content of stdin\n");
      exit(1);
    }
  }

  /* 5th step: process the list of full paths */
  for (int i = reverse_mode ? (num_full_paths - 1) : 0;
       reverse_mode ? (i >= 0) : (i < num_full_paths); reverse_mode ? i-- : i++) {
    char *filename = full_paths[i];
    if (debug_mode)
      fprintf(stderr, "processing: %s\n", filename);
    int result = stat(filename, &st);
    if (result < 0) {
      error("failed to stat component %s: %s", filename, strerror(errno));
      if (exit_on_error_mode) {
        exit(1);
      }
      else
        continue;
    }

    if (S_ISREG(st.st_mode)) {
      if (!access(filename, X_OK)) {
	if (test_mode) {
	  printf("%s\n", filename);
	}
	else if (list_mode) {
	  if (!access(filename, R_OK))
	    printf("%s\n", filename);
	}
	else {
	  if (verbose_mode) {
	    if (argcount) {
	      char **a = args;

	      fprintf(stderr, "run-parts: executing %s", filename);
	      while(*(++a))
		fprintf(stderr, " %s", *a);
	      fprintf(stderr, "\n");
	    } else {
	      fprintf(stderr, "run-parts: executing %s\n", filename);
	    }
	  }
	  run_part(filename);
	  if (exitstatus != 0 && exit_on_error_mode) return;
	}
      }
      else if (!access(filename, R_OK)) {
	if (list_mode) {
	  printf("%s\n", filename);
	}
      }
      else if (S_ISLNK(st.st_mode)) {
	if (!list_mode) {
	  error("run-parts: component %s is a broken symbolic link\n",filename);
	  exitstatus = 1;
	}
      }
    }
    else if (!S_ISDIR(st.st_mode)) {
      if (!list_mode) {
	error("run-parts: component %s is not an executable plain file\n",
	       filename);
	exitstatus = 1;
      }
    }

  }

  if (full_paths != NULL) {
    for (int i = 0; i < num_full_paths; i++) {
      free(full_paths[i]);
    }
    free(full_paths);
  }

  if (basenames != NULL) {
    for (int i = 0; i < num_basenames; i++) {
      free(basenames[i]);
    }
    free(basenames);
  }

}

/* Process options */
int main(int argc, char *argv[])
{
  custom_ere = NULL;
  umask(022);
  add_argument(0);

  for (;;) {
    int c;
    int option_index = 0;

    static struct option long_options[] = {
      {"test", 0, &test_mode, 1},
      {"list", 0, &list_mode, 1},
      {"verbose", 0, 0, 'v'},
      {"debug", 0, 0, 'd'},
      {"report", 0, &report_mode, 1},
      {"reverse", 0, &reverse_mode, 1},
      {"umask", 1, 0, 'u'},
      {"arg", 1, 0, 'a'},
      {"help", 0, 0, 'h'},
      {"version", 0, 0, 'V'},
      {"lsbsysinit", 0, &regex_mode, RUNPARTS_LSBSYSINIT},
      {"regex", 1, &regex_mode, RUNPARTS_ERE},
      {"stdin", 0, &stdin_mode, 1},
      {"exit-on-error", 0, &exit_on_error_mode, 1},
      {"new-session", 0, &new_session_mode, 1},
      {"after", 1, 0, 'A'},
      {"before", 1, 0, 'B'},
      {0, 0, 0, 0}
    };

    c = getopt_long(argc, argv, "u:ha:A:B:vVd", long_options, &option_index);
    if (c == EOF)
      break;
    switch (c) {
    case 0:
      if(option_index==11) { /* hardcoding this will lead to trouble */
        custom_ere = strdup(optarg);
      }
      break;
    case 'u':
      set_umask();
      break;
    case 'a':
      add_argument(optarg);
      break;
    case 'h':
      usage();
      break;
    case 'v':
      verbose_mode = 1;
      break;
    case 'd':
      debug_mode = 1;
      break;
    case 'A':
      run_after = optarg;
      break;
    case 'B':
      run_before = optarg;
      break;
    case 'V':
      version();
      break;
    default:
      fprintf(stderr, "Try `run-parts --help' for more information.\n");
      exit(1);
    }
  }

  /* We require exactly one argument: the directory name */
  if (optind == argc) {
    error("missing operand");
    fprintf(stderr, "Try `run-parts --help' for more information.\n");
    exit(1);
  }

  if (list_mode && test_mode) {
    error("--list and --test can not be used together");
    fprintf(stderr, "Try `run-parts --help' for more information.\n");
    exit(1);
  }

  catch_signals();
  regex_compile_pattern();
  run_parts(argv+optind);
  regex_clean();

  free(args);
  free(custom_ere);

  return exitstatus;
}

/*
 * Compile patterns used by the application
 *
 * In order for a string to be matched by a pattern, this pattern must be
 * compiled with the regcomp function. If an error occurs, the application
 * exits and displays the error.
 */
static void
regex_compile_pattern (void)
{
    int      err;
    regex_t *pt_regex;

    if (regex_mode == RUNPARTS_ERE) {

        if ((err = regcomp(&customre, custom_ere,
                    REG_EXTENDED | REG_NOSUB)) != 0)
            pt_regex = &customre;

    } else if (regex_mode == RUNPARTS_LSBSYSINIT) {

        if ( (err = regcomp(&hierre, "^_?([a-z0-9_.]+-)+[a-z0-9]+$",
                    REG_EXTENDED | REG_NOSUB)) != 0)
            pt_regex = &hierre;

        else if ( (err = regcomp(&excsre, "^[a-z0-9-].*\\.dpkg-(old|dist|new|tmp)$",
                    REG_EXTENDED | REG_NOSUB)) != 0)
            pt_regex = &excsre;

        else if ( (err = regcomp(&tradre, "^[a-z0-9][a-z0-9_-]*$", REG_NOSUB))
                    != 0)
            pt_regex = &tradre;

    } else if ( (err = regcomp(&classicalre, "^[a-zA-Z0-9_-]+$",
                    REG_EXTENDED | REG_NOSUB)) != 0)
        pt_regex = &classicalre;

    if (err != 0) {
        fprintf(stderr, "Unable to build regexp: %s\n", \
                            regex_get_error(err, pt_regex));
        exit(1);
    }
}

/*
 * Get a regex error.
 *
 * This function allocates a buffer to store the regex error description.
 * If a buffer cannot be allocated, then the use of xmalloc will end the
 * program.
 *
 * @errcode: return error code from a one of the regex functions
 * @compiled: compile pattern which causes the failure
 *
 * It returns a pointer on the current regex error description.
 */
static char *
regex_get_error(int errcode, regex_t *compiled)
{
    size_t  length;
    char     *buf;

    length = regerror(errcode, compiled, NULL, 0);
    buf    = malloc(length);
    if (buf == 0) {
        error("Virtual memory exhausted\n");
        exit(1);
    }

    regerror(errcode, compiled, buf, length);

    return buf;
}

/*
 * Clean the compiled patterns according to the current regex_mode
 */
static void
regex_clean(void)
{
    if (regex_mode == RUNPARTS_ERE)
        regfree(&customre);

    else if (regex_mode == RUNPARTS_LSBSYSINIT) {
        regfree(&hierre);
        regfree(&excsre);
        regfree(&tradre);

    } else
        regfree(&classicalre);
}
