1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * CRONTAB
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4 | *
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5 | * usually setuid root, -c option only works if getuid() == geteuid()
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6 | *
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7 | * Copyright 1994 Matthew Dillon (dillon@apollo.west.oic.com)
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8 | * Vladimir Oleynik <dzo@simtreas.ru> (C) 2002
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9 | *
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10 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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11 | */
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12 |
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13 | #include "libbb.h"
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14 |
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15 | #define CRONTABS CONFIG_FEATURE_CROND_DIR "/crontabs"
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16 | #ifndef CRONUPDATE
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17 | #define CRONUPDATE "cron.update"
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18 | #endif
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19 |
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20 | static void edit_file(const struct passwd *pas, const char *file)
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21 | {
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22 | const char *ptr;
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23 | int pid = xvfork();
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24 |
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25 | if (pid) { /* parent */
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26 | wait4pid(pid);
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27 | return;
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28 | }
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29 |
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30 | /* CHILD - change user and run editor */
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31 | /* initgroups, setgid, setuid */
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32 | change_identity(pas);
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33 | setup_environment(DEFAULT_SHELL,
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34 | SETUP_ENV_CHANGEENV | SETUP_ENV_TO_TMP,
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35 | pas);
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36 | ptr = getenv("VISUAL");
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37 | if (!ptr) {
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38 | ptr = getenv("EDITOR");
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39 | if (!ptr)
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40 | ptr = "vi";
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41 | }
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42 |
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43 | BB_EXECLP(ptr, ptr, file, NULL);
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44 | bb_perror_msg_and_die("exec %s", ptr);
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45 | }
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46 |
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47 | static int open_as_user(const struct passwd *pas, const char *file)
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48 | {
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49 | pid_t pid;
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50 | char c;
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51 |
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52 | pid = xvfork();
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53 | if (pid) { /* PARENT */
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54 | if (wait4pid(pid) == 0) {
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55 | /* exitcode 0: child says it can read */
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56 | return open(file, O_RDONLY);
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57 | }
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58 | return -1;
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59 | }
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60 |
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61 | /* CHILD */
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62 | /* initgroups, setgid, setuid */
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63 | change_identity(pas);
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64 | /* We just try to read one byte. If it works, file is readable
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65 | * under this user. We signal that by exiting with 0. */
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66 | _exit(safe_read(xopen(file, O_RDONLY), &c, 1) < 0);
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67 | }
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68 |
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69 | int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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70 | int crontab_main(int argc UNUSED_PARAM, char **argv)
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71 | {
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72 | const struct passwd *pas;
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73 | const char *crontab_dir = CRONTABS;
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74 | char *tmp_fname;
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75 | char *new_fname;
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76 | char *user_name; /* -u USER */
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77 | int fd;
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78 | int src_fd;
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79 | int opt_ler;
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80 |
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81 | /* file [opts] Replace crontab from file
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82 | * - [opts] Replace crontab from stdin
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83 | * -u user User
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84 | * -c dir Crontab directory
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85 | * -l List crontab for user
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86 | * -e Edit crontab for user
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87 | * -r Delete crontab for user
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88 | * bbox also supports -d == -r, but most other crontab
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89 | * implementations do not. Deprecated.
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90 | */
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91 | enum {
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92 | OPT_u = (1 << 0),
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93 | OPT_c = (1 << 1),
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94 | OPT_l = (1 << 2),
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95 | OPT_e = (1 << 3),
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96 | OPT_r = (1 << 4),
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97 | OPT_ler = OPT_l + OPT_e + OPT_r,
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98 | };
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99 |
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100 | opt_complementary = "?1:dr"; /* max one argument; -d implies -r */
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101 | opt_ler = getopt32(argv, "u:c:lerd", &user_name, &crontab_dir);
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102 | argv += optind;
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103 |
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104 | if (sanitize_env_if_suid()) { /* Clears dangerous stuff, sets PATH */
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105 | /* Run by non-root */
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106 | if (opt_ler & (OPT_u|OPT_c))
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107 | bb_error_msg_and_die(bb_msg_you_must_be_root);
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108 | }
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109 |
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110 | if (opt_ler & OPT_u) {
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111 | pas = xgetpwnam(user_name);
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112 | } else {
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113 | pas = xgetpwuid(getuid());
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114 | }
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115 |
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116 | #define user_name DONT_USE_ME_BEYOND_THIS_POINT
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117 |
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118 | /* From now on, keep only -l, -e, -r bits */
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119 | opt_ler &= OPT_ler;
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120 | if ((opt_ler - 1) & opt_ler) /* more than one bit set? */
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121 | bb_show_usage();
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122 |
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123 | /* Read replacement file under user's UID/GID/group vector */
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124 | src_fd = STDIN_FILENO;
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125 | if (!opt_ler) { /* Replace? */
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126 | if (!argv[0])
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127 | bb_show_usage();
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128 | if (NOT_LONE_DASH(argv[0])) {
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129 | src_fd = open_as_user(pas, argv[0]);
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130 | if (src_fd < 0)
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131 | bb_error_msg_and_die("user %s cannot read %s",
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132 | pas->pw_name, argv[0]);
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133 | }
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134 | }
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135 |
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136 | /* cd to our crontab directory */
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137 | xchdir(crontab_dir);
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138 |
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139 | tmp_fname = NULL;
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140 |
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141 | /* Handle requested operation */
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142 | switch (opt_ler) {
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143 |
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144 | default: /* case OPT_r: Delete */
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145 | unlink(pas->pw_name);
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146 | break;
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147 |
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148 | case OPT_l: /* List */
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149 | {
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150 | char *args[2] = { pas->pw_name, NULL };
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151 | return bb_cat(args);
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152 | /* list exits,
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153 | * the rest go play with cron update file */
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154 | }
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155 |
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156 | case OPT_e: /* Edit */
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157 | tmp_fname = xasprintf("%s.%u", crontab_dir, (unsigned)getpid());
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158 | /* No O_EXCL: we don't want to be stuck if earlier crontabs
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159 | * were killed, leaving stale temp file behind */
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160 | src_fd = xopen3(tmp_fname, O_RDWR|O_CREAT|O_TRUNC, 0600);
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161 | fchown(src_fd, pas->pw_uid, pas->pw_gid);
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162 | fd = open(pas->pw_name, O_RDONLY);
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163 | if (fd >= 0) {
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164 | bb_copyfd_eof(fd, src_fd);
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165 | close(fd);
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166 | xlseek(src_fd, 0, SEEK_SET);
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167 | }
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168 | close_on_exec_on(src_fd); /* don't want editor to see this fd */
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169 | edit_file(pas, tmp_fname);
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170 | /* fall through */
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171 |
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172 | case 0: /* Replace (no -l, -e, or -r were given) */
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173 | new_fname = xasprintf("%s.new", pas->pw_name);
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174 | fd = open(new_fname, O_WRONLY|O_CREAT|O_TRUNC|O_APPEND, 0600);
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175 | if (fd >= 0) {
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176 | bb_copyfd_eof(src_fd, fd);
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177 | close(fd);
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178 | xrename(new_fname, pas->pw_name);
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179 | } else {
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180 | bb_error_msg("can't create %s/%s",
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181 | crontab_dir, new_fname);
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182 | }
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183 | if (tmp_fname)
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184 | unlink(tmp_fname);
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185 | /*free(tmp_fname);*/
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186 | /*free(new_fname);*/
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187 |
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188 | } /* switch */
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189 |
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190 | /* Bump notification file. Handle window where crond picks file up
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191 | * before we can write our entry out.
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192 | */
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193 | while ((fd = open(CRONUPDATE, O_WRONLY|O_CREAT|O_APPEND, 0600)) >= 0) {
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194 | struct stat st;
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195 |
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196 | fdprintf(fd, "%s\n", pas->pw_name);
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197 | if (fstat(fd, &st) != 0 || st.st_nlink != 0) {
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198 | /*close(fd);*/
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199 | break;
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200 | }
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201 | /* st.st_nlink == 0:
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202 | * file was deleted, maybe crond missed our notification */
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203 | close(fd);
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204 | /* loop */
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205 | }
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206 | if (fd < 0) {
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207 | bb_error_msg("can't append to %s/%s",
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208 | crontab_dir, CRONUPDATE);
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209 | }
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210 | return 0;
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211 | }
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