| 1 | /* |
| 2 | * after: wait for an unrelated process to terminate, returning |
| 3 | * its exit code if possible. |
| 4 | */ |
| 5 | |
| 6 | /* |
| 7 | * Possible future extensions: |
| 8 | * |
| 9 | * - improvements to existing methods |
| 10 | * * the ptrace method on MacOS has the really unpleasant |
| 11 | * property that if after is interrupted or killed then the |
| 12 | * traced process dies too. We could mitigate that by |
| 13 | * trapping some common fatal signals (certainly including |
| 14 | * SIGINT and SIGTERM) and have them PT_DETACH before |
| 15 | * self-reraising. Alternatively, we could fork off a |
| 16 | * subprocess to do the tracing, and a pipe communicating |
| 17 | * with the parent; then if the subprocess detected its pipe |
| 18 | * end being closed it could PT_DETACH. Then even kill -9 |
| 19 | * against the primary `after' process would allow the |
| 20 | * subprocess to clean up. |
| 21 | * |
| 22 | * - alternatives to ptrace on systems supporting different |
| 23 | * process-debugging mechanisms |
| 24 | * |
| 25 | * - possibly an approach based on invoking ps? |
| 26 | * * with a longish interval, to prevent system overload |
| 27 | * * and we have to deal with the profusion of ps options. I |
| 28 | * suspect going by SUS/POSIX is the best thing here: set |
| 29 | * POSIXLY_CORRECT and expect ps to support the options |
| 30 | * given in SUS. |
| 31 | * * need to try to avoid race condition if the process ends |
| 32 | * and another one of the same name starts up. Printing the |
| 33 | * start time seems like the sensible thing, except that SUS |
| 34 | * doesn't give a standard option to do that; we can only |
| 35 | * print elapsed time since the process began, which means |
| 36 | * we have to be alert for off-by-1s errors if we wait 30s |
| 37 | * and the time only changes by 29 for some irritating |
| 38 | * reason. |
| 39 | */ |
| 40 | |
| 41 | #include <stdio.h> |
| 42 | #include <stdlib.h> |
| 43 | #include <string.h> |
| 44 | #include <ctype.h> |
| 45 | #include <errno.h> |
| 46 | |
| 47 | #include <unistd.h> |
| 48 | #include <sys/types.h> |
| 49 | #include <sys/wait.h> |
| 50 | |
| 51 | char errbuf[4096]; |
| 52 | int errlen = 0; |
| 53 | char *pname; |
| 54 | |
| 55 | #ifndef NO_PTRACE |
| 56 | |
| 57 | /* |
| 58 | * ptrace-based waiting method, which gets the process's exit |
| 59 | * code. |
| 60 | */ |
| 61 | |
| 62 | #include <sys/ptrace.h> |
| 63 | |
| 64 | #if !defined PTRACE_FLAVOUR_LINUX && !defined PTRACE_FLAVOUR_BSD |
| 65 | /* |
| 66 | * Attempt to autodetect ptrace flavour. |
| 67 | */ |
| 68 | #if defined PTRACE_ATTACH |
| 69 | |
| 70 | /* |
| 71 | * Linux flavour. |
| 72 | */ |
| 73 | #define ATTACH_TO(pid) ptrace(PTRACE_ATTACH, pid, NULL, 0) |
| 74 | #define ATTACH_STR "ptrace(PTRACE_ATTACH, %d)" |
| 75 | #define CONTINUE(pid) ptrace(PTRACE_CONT, pid, NULL, 0) |
| 76 | #define CONT_STR "ptrace(PTRACE_CONT, %d)" |
| 77 | |
| 78 | #elif defined PT_ATTACH |
| 79 | |
| 80 | /* |
| 81 | * BSD/MacOS flavour. |
| 82 | */ |
| 83 | #define ATTACH_TO(pid) ptrace(PT_ATTACH, pid, NULL, 0) |
| 84 | #define ATTACH_STR "ptrace(PT_ATTACH, %d)" |
| 85 | #define CONTINUE(pid) ptrace(PT_CONTINUE, pid, (caddr_t)1, 0) |
| 86 | #define CONT_STR "ptrace(PT_CONTINUE, %d)" |
| 87 | |
| 88 | #else |
| 89 | #error Unable to autodetect ptrace flavour. |
| 90 | #endif /* ptrace flavour detection */ |
| 91 | |
| 92 | #endif /* outer ifdef containing flavour detection */ |
| 93 | |
| 94 | int after_ptrace(int pid) |
| 95 | { |
| 96 | if ( |
| 97 | #ifdef PTRACE_FLAVOUR_LINUX |
| 98 | ptrace(PTRACE_ATTACH, pid, NULL, 0) |
| 99 | #else |
| 100 | ptrace(PT_ATTACH, pid, NULL, 0) |
| 101 | #endif |
| 102 | < 0) { |
| 103 | /* |
| 104 | * If we can't attach to the process, that's not a fatal |
| 105 | * error; it just means we fall back to the next available |
| 106 | * method. |
| 107 | */ |
| 108 | errlen += sprintf(errbuf+errlen, |
| 109 | "%s: "ATTACH_STR": %.256s\n", |
| 110 | pname, pid, strerror(errno)); |
| 111 | return -1; |
| 112 | } |
| 113 | |
| 114 | /* |
| 115 | * Having successfully attached to the process, however, any |
| 116 | * subsequent error is fatal. |
| 117 | */ |
| 118 | |
| 119 | while (1) { |
| 120 | int wpid, wstatus; |
| 121 | wpid = waitpid(pid, &wstatus, 0); |
| 122 | if (wpid < 0) { |
| 123 | perror("wait"); |
| 124 | return 127; |
| 125 | } else if (WIFEXITED(wstatus)) { |
| 126 | return WEXITSTATUS(wstatus); |
| 127 | } else { |
| 128 | if (CONTINUE(pid) < 0) { |
| 129 | fprintf(stderr, "%s: "CONT_STR": %.256s\n", |
| 130 | pname, pid, strerror(errno)); |
| 131 | return 127; |
| 132 | } |
| 133 | } |
| 134 | } |
| 135 | } |
| 136 | |
| 137 | #endif |
| 138 | |
| 139 | #ifndef NO_PROC |
| 140 | |
| 141 | /* |
| 142 | * /proc-based waiting method. |
| 143 | */ |
| 144 | |
| 145 | int after_proc(int pid) |
| 146 | { |
| 147 | char buf[128]; |
| 148 | |
| 149 | sprintf(buf, "/proc/%d", pid); |
| 150 | |
| 151 | if (chdir(buf) < 0) { |
| 152 | /* |
| 153 | * Fallback error. |
| 154 | */ |
| 155 | errlen += sprintf(errbuf+errlen, |
| 156 | "%s: chdir(\"%.32s\"): %.256s\n", |
| 157 | pname, buf, strerror(errno)); |
| 158 | return -1; |
| 159 | } |
| 160 | |
| 161 | do { |
| 162 | sleep(1); |
| 163 | } while (getcwd(buf, sizeof(buf))); |
| 164 | |
| 165 | return 0; |
| 166 | } |
| 167 | |
| 168 | #endif |
| 169 | |
| 170 | #ifdef NO_PTRACE |
| 171 | #define NO_EXITCODE |
| 172 | #endif |
| 173 | |
| 174 | const char usagemsg[] = |
| 175 | "usage: after" |
| 176 | #ifndef NO_EXITCODE |
| 177 | " [ -x | -z ]" |
| 178 | #endif |
| 179 | " <pid>\n" |
| 180 | #ifndef NO_EXITCODE |
| 181 | "where: -x return an error if the process's exit code is unavailable\n" |
| 182 | " -z return 0 instead of the process's exit code\n" |
| 183 | #endif |
| 184 | " also: after --version report version number\n" |
| 185 | " after --help display this help text\n" |
| 186 | " after --licence display the (MIT) licence text\n" |
| 187 | ; |
| 188 | |
| 189 | void usage(void) { |
| 190 | fputs(usagemsg, stdout); |
| 191 | } |
| 192 | |
| 193 | const char licencemsg[] = |
| 194 | "after is copyright 2008 Simon Tatham.\n" |
| 195 | "\n" |
| 196 | "Permission is hereby granted, free of charge, to any person\n" |
| 197 | "obtaining a copy of this software and associated documentation files\n" |
| 198 | "(the \"Software\"), to deal in the Software without restriction,\n" |
| 199 | "including without limitation the rights to use, copy, modify, merge,\n" |
| 200 | "publish, distribute, sublicense, and/or sell copies of the Software,\n" |
| 201 | "and to permit persons to whom the Software is furnished to do so,\n" |
| 202 | "subject to the following conditions:\n" |
| 203 | "\n" |
| 204 | "The above copyright notice and this permission notice shall be\n" |
| 205 | "included in all copies or substantial portions of the Software.\n" |
| 206 | "\n" |
| 207 | "THE SOFTWARE IS PROVIDED \"AS IS\", WITHOUT WARRANTY OF ANY KIND,\n" |
| 208 | "EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF\n" |
| 209 | "MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND\n" |
| 210 | "NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS\n" |
| 211 | "BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN\n" |
| 212 | "ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN\n" |
| 213 | "CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE\n" |
| 214 | "SOFTWARE.\n" |
| 215 | ; |
| 216 | |
| 217 | void licence(void) { |
| 218 | fputs(licencemsg, stdout); |
| 219 | } |
| 220 | |
| 221 | void version(void) { |
| 222 | #define SVN_REV "$Revision$" |
| 223 | char rev[sizeof(SVN_REV)]; |
| 224 | char *p, *q; |
| 225 | |
| 226 | strcpy(rev, SVN_REV); |
| 227 | |
| 228 | for (p = rev; *p && *p != ':'; p++); |
| 229 | if (*p) { |
| 230 | p++; |
| 231 | while (*p && isspace((unsigned char)*p)) p++; |
| 232 | for (q = p; *q && !isspace((unsigned char)*q) && *q != '$'; q++); |
| 233 | if (*q) *q = '\0'; |
| 234 | printf("after revision %s", p); |
| 235 | } else { |
| 236 | printf("after: unknown version"); |
| 237 | } |
| 238 | putchar('\n'); |
| 239 | } |
| 240 | |
| 241 | int main(int argc, char **argv) |
| 242 | { |
| 243 | int pid = -1; |
| 244 | enum { UNWANTED, OPTIONAL, MANDATORY } exitcode = OPTIONAL; |
| 245 | int ret; |
| 246 | |
| 247 | pname = argv[0]; |
| 248 | |
| 249 | /* parse the command line arguments */ |
| 250 | while (--argc) { |
| 251 | char *p = *++argv; |
| 252 | |
| 253 | #ifndef NO_EXITCODE |
| 254 | if (!strcmp(p, "-x")) { |
| 255 | exitcode = MANDATORY; |
| 256 | } else if (!strcmp(p, "-z")) { |
| 257 | exitcode = UNWANTED; |
| 258 | } else |
| 259 | #endif |
| 260 | if (!strcmp(p, "--help")) { |
| 261 | usage(); |
| 262 | return 0; |
| 263 | } else if (!strcmp(p, "--version")) { |
| 264 | version(); |
| 265 | return 0; |
| 266 | } else if (!strcmp(p, "--licence") || !strcmp(p, "--license")) { |
| 267 | licence(); |
| 268 | return 0; |
| 269 | } else if (*p=='-') { |
| 270 | fprintf(stderr, "%s: unrecognised option `%s'\n", pname, p); |
| 271 | return 1; |
| 272 | } else { |
| 273 | if (pid >= 0) { |
| 274 | fprintf(stderr, "%s: parameter `%s' unexpected\n", pname, p); |
| 275 | return 1; |
| 276 | } else { |
| 277 | pid = atoi(p); |
| 278 | } |
| 279 | } |
| 280 | } |
| 281 | |
| 282 | if (pid < 0) { |
| 283 | usage(); |
| 284 | return 0; |
| 285 | } |
| 286 | |
| 287 | #ifndef NO_PTRACE |
| 288 | ret = after_ptrace(pid); |
| 289 | if (ret >= 0) |
| 290 | return (exitcode == UNWANTED ? 0 : ret); |
| 291 | #endif |
| 292 | |
| 293 | if (exitcode == MANDATORY) { |
| 294 | /* |
| 295 | * If we reach here, the user has demanded the process's |
| 296 | * return code, and we haven't been able to get it. Print |
| 297 | * the error messages we accrued while trying, and abandon |
| 298 | * ship. |
| 299 | */ |
| 300 | fputs(errbuf, stderr); |
| 301 | return 127; |
| 302 | } |
| 303 | |
| 304 | #ifndef NO_PROC |
| 305 | ret = after_proc(pid); |
| 306 | if (ret >= 0) |
| 307 | return ret; |
| 308 | #endif |
| 309 | |
| 310 | /* |
| 311 | * If we reach here, we have run out of all our options. Print |
| 312 | * all our error messages, and return total failure. |
| 313 | */ |
| 314 | fputs(errbuf, stderr); |
| 315 | return 127; |
| 316 | } |