xref: /freebsd/usr.bin/limits/limits.c (revision c17d43407fe04133a94055b0dbc7ea8965654a9f)
1 /*-
2  * Copyright (c) 1997 by
3  * David L. Nugent <davidn@blaze.net.au>
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, is permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice immediately at the beginning of the file, without modification,
11  *    this list of conditions, and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. This work was done expressly for inclusion into FreeBSD.  Other use
16  *    is permitted provided this notation is included.
17  * 4. Absolutely no warranty of function or purpose is made by the authors.
18  * 5. Modifications may be freely made to this file providing the above
19  *    conditions are met.
20  *
21  * Display/change(+runprogram)/eval resource limits.
22  *
23  * $FreeBSD$
24  */
25 
26 #include <err.h>
27 #include <stdio.h>
28 #include <string.h>
29 #include <sys/types.h>
30 #include <sys/stat.h>
31 #include <sys/param.h>
32 #include <stdlib.h>
33 #include <unistd.h>
34 #include <stdarg.h>
35 #include <ctype.h>
36 #include <errno.h>
37 #include <pwd.h>
38 #include <login_cap.h>
39 #include <sys/time.h>
40 #include <sys/resource.h>
41 
42 enum
43 {
44     SH_NONE,
45     SH_SH,      /* sh */
46     SH_CSH,     /* csh */
47     SH_BASH,    /* gnu bash */
48     SH_TCSH,    /* tcsh */
49     SH_KSH,     /* (pd)ksh */
50     SH_ZSH,     /* zsh */
51     SH_RC,      /* rc or es */
52     SH_NUMBER
53 };
54 
55 
56 /* eval emitter for popular shells.
57  * Why aren't there any standards here? Most shells support either
58  * the csh 'limit' or sh 'ulimit' command, but each varies just
59  * enough that they aren't very compatible from one to the other.
60  */
61 static struct {
62     const char * name;	    /* Name of shell */
63     const char * inf;	    /* Name used for 'unlimited' resource */
64     const char * cmd;	    /* Intro text */
65     const char * hard;	    /* Hard limit text */
66     const char * soft;	    /* Soft limit text */
67     const char * both;	    /* Hard+Soft limit text */
68     struct {
69 	const char * pfx;
70 	const char * sfx;
71 	int divisor;
72     } lprm[RLIM_NLIMITS];
73 } shellparm[] =
74 {
75     { "", "infinity", "Resource limits%s%s:\n", "-max", "-cur", "",
76       {
77 	  { "  cputime%-4s      %8s", " secs\n",  1    },
78 	  { "  filesize%-4s     %8s", " kb\n",    1024 },
79 	  { "  datasize%-4s     %8s", " kb\n",    1024 },
80 	  { "  stacksize%-4s    %8s", " kb\n",    1024 },
81 	  { "  coredumpsize%-4s %8s", " kb\n",    1024 },
82 	  { "  memoryuse%-4s    %8s", " kb\n",    1024 },
83 	  { "  memorylocked%-4s %8s", " kb\n",    1024 },
84 	  { "  maxprocesses%-4s %8s", "\n",       1    },
85 	  { "  openfiles%-4s    %8s", "\n",       1    },
86 	  { "  sbsize%-4s       %8s", " bytes\n", 1    }
87       }
88     },
89     { "sh", "unlimited", "", " -H", " -S", "",
90       {
91 	  { "ulimit%s -t %s", ";\n",  1    },
92 	  { "ulimit%s -f %s", ";\n",  512  },
93 	  { "ulimit%s -d %s", ";\n",  1024 },
94 	  { "ulimit%s -s %s", ";\n",  1024 },
95 	  { "ulimit%s -c %s", ";\n",  512  },
96 	  { "ulimit%s -m %s", ";\n",  1024 },
97 	  { "ulimit%s -l %s", ";\n",  1024 },
98 	  { "ulimit%s -u %s", ";\n",  1    },
99 	  { "ulimit%s -n %s", ";\n",  1    },
100 	  { "ulimit%s -b %s", ";\n",  1    }
101       }
102     },
103     { "csh", "unlimited", "", " -h", "", NULL,
104       {
105 	  { "limit%s cputime %s",      ";\n",  1    },
106 	  { "limit%s filesize %s",     ";\n",  1024 },
107 	  { "limit%s datasize %s",     ";\n",  1024 },
108 	  { "limit%s stacksize %s",    ";\n",  1024 },
109 	  { "limit%s coredumpsize %s", ";\n",  1024 },
110 	  { "limit%s memoryuse %s",    ";\n",  1024 },
111 	  { "limit%s memorylocked %s", ";\n",  1024 },
112 	  { "limit%s maxproc %s",      ";\n",  1    },
113 	  { "limit%s openfiles %s",    ";\n",  1    },
114 	  { "limit%s sbsize %s",       ";\n",  1    }
115       }
116     },
117     { "bash|bash2", "unlimited", "", " -H", " -S", "",
118       {
119 	  { "ulimit%s -t %s", ";\n",  1    },
120 	  { "ulimit%s -f %s", ";\n",  1024 },
121 	  { "ulimit%s -d %s", ";\n",  1024 },
122 	  { "ulimit%s -s %s", ";\n",  1024 },
123 	  { "ulimit%s -c %s", ";\n",  1024 },
124 	  { "ulimit%s -m %s", ";\n",  1024 },
125 	  { "ulimit%s -l %s", ";\n",  1024 },
126 	  { "ulimit%s -u %s", ";\n",  1    },
127 	  { "ulimit%s -n %s", ";\n",  1    },
128 	  { "ulimit%s -b %s", ";\n",  1    }
129       }
130     },
131     { "tcsh", "unlimited", "", " -h", "", NULL,
132       {
133 	  { "limit%s cputime %s",      ";\n",  1    },
134 	  { "limit%s filesize %s",     ";\n",  1024 },
135 	  { "limit%s datasize %s",     ";\n",  1024 },
136 	  { "limit%s stacksize %s",    ";\n",  1024 },
137 	  { "limit%s coredumpsize %s", ";\n",  1024 },
138 	  { "limit%s memoryuse %s",    ";\n",  1024 },
139 	  { "limit%s memorylocked %s", ";\n",  1024 },
140 	  { "limit%s maxproc %s",      ";\n",  1    },
141 	  { "limit%s descriptors %s",  ";\n",  1    },
142 	  { "limit%s sbsize %s",       ";\n",  1    }
143       }
144     },
145     { "ksh|pdksh", "unlimited", "", " -H", " -S", "",
146       {
147 	  { "ulimit%s -t %s", ";\n",  1    },
148 	  { "ulimit%s -f %s", ";\n",  512  },
149 	  { "ulimit%s -d %s", ";\n",  1024 },
150 	  { "ulimit%s -s %s", ";\n",  1024 },
151 	  { "ulimit%s -c %s", ";\n",  512  },
152 	  { "ulimit%s -m %s", ";\n",  1024 },
153 	  { "ulimit%s -l %s", ";\n",  1024 },
154 	  { "ulimit%s -p %s", ";\n",  1    },
155 	  { "ulimit%s -n %s", ";\n",  1    },
156 	  { "ulimit%s -b %s", ";\n",  1    }
157       }
158     },
159     { "zsh", "unlimited", "", " -H", " -S", "",
160       {
161 	  { "ulimit%s -t %s", ";\n",  1    },
162 	  { "ulimit%s -f %s", ";\n",  512  },
163 	  { "ulimit%s -d %s", ";\n",  1024 },
164 	  { "ulimit%s -s %s", ";\n",  1024 },
165 	  { "ulimit%s -c %s", ";\n",  512  },
166 	  { "ulimit%s -m %s", ";\n",  1024 },
167 	  { "ulimit%s -l %s", ";\n",  1024 },
168 	  { "ulimit%s -u %s", ";\n",  1    },
169 	  { "ulimit%s -n %s", ";\n",  1    },
170 	  { "ulimit%s -b %s", ";\n",  1    }
171       }
172     },
173     { "rc|es", "unlimited", "", " -h", "", NULL,
174       {
175 	  { "limit%s cputime %s",      ";\n",  1    },
176 	  { "limit%s filesize %s",     ";\n",  1024 },
177 	  { "limit%s datasize %s",     ";\n",  1024 },
178 	  { "limit%s stacksize %s",    ";\n",  1024 },
179 	  { "limit%s coredumpsize %s", ";\n",  1024 },
180 	  { "limit%s memoryuse %s",    ";\n",  1024 },
181 	  { "limit%s lockedmemory %s", ";\n",  1024 },
182 	  { "limit%s processes %s",    ";\n",  1    },
183 	  { "limit%s descriptors %s",  ";\n",  1    },
184 	  { "limit%s sbsize %s",       ";\n",  1    }
185       }
186     },
187     { NULL }
188 };
189 
190 static struct {
191     const char * cap;
192     rlim_t (*func)(login_cap_t *, const char *, rlim_t, rlim_t);
193 } resources[RLIM_NLIMITS] = {
194     { "cputime",	login_getcaptime },
195     { "filesize",	login_getcapsize },
196     { "datasize",	login_getcapsize },
197     { "stacksize",	login_getcapsize },
198     { "coredumpsize",	login_getcapsize },
199     { "memoryuse",	login_getcapsize },
200     { "memorylocked",	login_getcapsize },
201     { "maxproc",	login_getcapnum  },
202     { "openfiles",	login_getcapnum  },
203     { "sbsize",		login_getcapsize  }
204 };
205 
206 /*
207  * One letter for each resource levels.
208  * NOTE: There is a dependancy on the corresponding
209  * letter index being equal to the resource number.
210  * If sys/resource.h defines are changed, this needs
211  * to be modified accordingly!
212  */
213 
214 #define RCS_STRING  "tfdscmlunb"
215 
216 static rlim_t resource_num(int which, int ch, const char *str);
217 static void usage(void);
218 static int getshelltype(void);
219 static void print_limit(rlim_t limit, unsigned divisor, const char *inf,
220 			const char *pfx, const char *sfx, const char *which);
221 extern char **environ;
222 
223 static const char rcs_string[] = RCS_STRING;
224 
225 int
226 main(int argc, char *argv[])
227 {
228     char *p, *cls = NULL;
229     char *cleanenv[1];
230     struct passwd * pwd = NULL;
231     int rcswhich, shelltype;
232     int i, num_limits = 0;
233     int ch, doeval = 0, doall = 0;
234     login_cap_t * lc = NULL;
235     enum { ANY=0, SOFT=1, HARD=2, BOTH=3, DISPLAYONLY=4 } type = ANY;
236     enum { RCSUNKNOWN=0, RCSSET=1, RCSSEL=2 } todo = RCSUNKNOWN;
237     int which_limits[RLIM_NLIMITS];
238     rlim_t set_limits[RLIM_NLIMITS];
239     struct rlimit limits[RLIM_NLIMITS];
240 
241     /* init resource tables */
242     for (i = 0; i < RLIM_NLIMITS; i++) {
243 	which_limits[i] = 0; /* Don't set/display any */
244 	set_limits[i] = RLIM_INFINITY;
245 	/* Get current resource values */
246 	getrlimit(i, &limits[i]);
247     }
248 
249     optarg = NULL;
250     while ((ch = getopt(argc, argv, ":EeC:U:BSHabc:d:f:l:m:n:s:t:u:")) != -1) {
251 	switch(ch) {
252 	case 'a':
253 	    doall = 1;
254 	    break;
255 	case 'E':
256 	    environ = cleanenv;
257 	    cleanenv[0] = NULL;
258 	    break;
259 	case 'e':
260 	    doeval = 1;
261 	    break;
262 	case 'C':
263 	    cls = optarg;
264 	    break;
265 	case 'U':
266 	    if ((pwd = getpwnam(optarg)) == NULL) {
267 		if (!isdigit(*optarg) ||
268 		    (pwd = getpwuid(atoi(optarg))) == NULL) {
269 		    warnx("invalid user `%s'", optarg);
270 		    usage();
271 		}
272 	    }
273 	    break;
274 	case 'H':
275 	    type = HARD;
276 	    break;
277 	case 'S':
278 	    type = SOFT;
279 	    break;
280 	case 'B':
281 	    type = SOFT|HARD;
282 	    break;
283 	default:
284 	case ':': /* Without arg */
285 	    if ((p = strchr(rcs_string, optopt)) != NULL) {
286 		int rcswhich = p - rcs_string;
287 		if (optarg && *optarg == '-') { /* 'arg' is actually a switch */
288 		    --optind;		/* back one arg, and make arg NULL */
289 		    optarg = NULL;
290 		}
291 		todo = optarg == NULL ? RCSSEL : RCSSET;
292 		if (type == ANY)
293 		    type = BOTH;
294 		which_limits[rcswhich] = optarg ? type : DISPLAYONLY;
295 		set_limits[rcswhich] = resource_num(rcswhich, optopt, optarg);
296 		num_limits++;
297 		break;
298 	    }
299 	    /* FALLTHRU */
300 	case '?':
301 	    usage();
302 	}
303 	optarg = NULL;
304     }
305 
306     /* If user was specified, get class from that */
307     if (pwd != NULL)
308 	lc = login_getpwclass(pwd);
309     else if (cls != NULL && *cls != '\0') {
310 	lc = login_getclassbyname(cls, NULL);
311 	if (lc == NULL || strcmp(cls, lc->lc_class) != 0)
312 	    fprintf(stderr, "login class '%s' non-existent, using %s\n",
313 		    cls, lc?lc->lc_class:"current settings");
314     }
315 
316     /* If we have a login class, update resource table from that */
317     if (lc != NULL) {
318 	for (rcswhich = 0; rcswhich < RLIM_NLIMITS; rcswhich++) {
319 	    char str[40];
320 	    rlim_t val;
321 
322 	    /* current value overridden by resourcename or resourcename-cur */
323 	    sprintf(str, "%s-cur", resources[rcswhich].cap);
324 	    val = resources[rcswhich].func(lc, resources[rcswhich].cap, limits[rcswhich].rlim_cur, limits[rcswhich].rlim_cur);
325 	    limits[rcswhich].rlim_cur = resources[rcswhich].func(lc, str, val, val);
326 	    /* maximum value overridden by resourcename or resourcename-max */
327 	    sprintf(str, "%s-max", resources[rcswhich].cap);
328 	    val = resources[rcswhich].func(lc, resources[rcswhich].cap, limits[rcswhich].rlim_max, limits[rcswhich].rlim_max);
329 	    limits[rcswhich].rlim_max = resources[rcswhich].func(lc, str, val, val);
330 	}
331     }
332 
333     /* now, let's determine what we wish to do with all this */
334 
335     argv += optind;
336 
337     /* If we're setting limits or doing an eval (ie. we're not just
338      * displaying), then check that hard limits are not lower than
339      * soft limits, and force rasing the hard limit if we need to if
340      * we are raising the soft limit, or lower the soft limit if we
341      * are lowering the hard limit.
342      */
343     if ((*argv || doeval) && getuid() == 0) {
344 
345 	for (rcswhich = 0; rcswhich < RLIM_NLIMITS; rcswhich++) {
346 	    if (limits[rcswhich].rlim_max != RLIM_INFINITY) {
347 		if (limits[rcswhich].rlim_cur == RLIM_INFINITY) {
348 		    limits[rcswhich].rlim_max = RLIM_INFINITY;
349 		    which_limits[rcswhich] |= HARD;
350 		} else if (limits[rcswhich].rlim_cur > limits[rcswhich].rlim_max) {
351 		    if (which_limits[rcswhich] == SOFT) {
352 			limits[rcswhich].rlim_max = limits[rcswhich].rlim_cur;
353 			which_limits[rcswhich] |= HARD;
354 		    }  else if (which_limits[rcswhich] == HARD) {
355 			limits[rcswhich].rlim_cur = limits[rcswhich].rlim_max;
356 			which_limits[rcswhich] |= SOFT;
357 		    } else {
358 			/* else.. if we're specifically setting both to
359 			 * silly values, then let it error out.
360 			 */
361 		    }
362 		}
363 	    }
364 	}
365     }
366 
367     /* See if we've overridden anything specific on the command line */
368     if (num_limits && todo == RCSSET) {
369 	for (rcswhich = 0; rcswhich < RLIM_NLIMITS; rcswhich++) {
370 	    if (which_limits[rcswhich] & HARD)
371 		limits[rcswhich].rlim_max = set_limits[rcswhich];
372 	    if (which_limits[rcswhich] & SOFT)
373 		limits[rcswhich].rlim_cur = set_limits[rcswhich];
374 	}
375     }
376 
377     /* If *argv is not NULL, then we are being asked to
378      * (perhaps) set environment variables and run a program
379      */
380     if (*argv) {
381 	if (doeval) {
382 	    warnx("-e cannot be used with `cmd' option");
383 	    usage();
384 	}
385 
386 	login_close(lc);
387 
388 	/* set leading environment variables, like eval(1) */
389 	while (*argv && (p = strchr(*argv, '=')))
390 	    (void)setenv(*argv++, ++p, 1);
391 
392 	/* Set limits */
393 	for (rcswhich = 0; rcswhich < RLIM_NLIMITS; rcswhich++) {
394 	    if (doall || num_limits == 0 || which_limits[rcswhich] != 0)
395 		if (setrlimit(rcswhich, &limits[rcswhich]) == -1)
396 		    err(1, "setrlimit %s", resources[rcswhich].cap);
397 	}
398 
399 	if (*argv == NULL)
400 	    usage();
401 
402 	execvp(*argv, argv);
403 	err(1, "%s", *argv);
404     }
405 
406     shelltype = doeval ? getshelltype() : SH_NONE;
407 
408     if (type == ANY) /* Default to soft limits */
409 	type = SOFT;
410 
411     /* Display limits */
412     printf(shellparm[shelltype].cmd,
413 	   lc ? " for class " : " (current)",
414 	   lc ? lc->lc_class : "");
415 
416     for (rcswhich = 0; rcswhich < RLIM_NLIMITS; rcswhich++) {
417 	if (doall || num_limits == 0 || which_limits[rcswhich] != 0) {
418 	    if (which_limits[rcswhich] == ANY || which_limits[rcswhich])
419 		which_limits[rcswhich] = type;
420 	    if (shellparm[shelltype].lprm[rcswhich].pfx) {
421 		if (shellparm[shelltype].both && limits[rcswhich].rlim_cur == limits[rcswhich].rlim_max) {
422 		    print_limit(limits[rcswhich].rlim_max,
423 				shellparm[shelltype].lprm[rcswhich].divisor,
424 				shellparm[shelltype].inf,
425 				shellparm[shelltype].lprm[rcswhich].pfx,
426 				shellparm[shelltype].lprm[rcswhich].sfx,
427 				shellparm[shelltype].both);
428 		} else {
429 		    if (which_limits[rcswhich] & HARD) {
430 			print_limit(limits[rcswhich].rlim_max,
431 				    shellparm[shelltype].lprm[rcswhich].divisor,
432 				    shellparm[shelltype].inf,
433 				    shellparm[shelltype].lprm[rcswhich].pfx,
434 				    shellparm[shelltype].lprm[rcswhich].sfx,
435 				    shellparm[shelltype].hard);
436 		    }
437 		    if (which_limits[rcswhich] & SOFT) {
438 			print_limit(limits[rcswhich].rlim_cur,
439 				    shellparm[shelltype].lprm[rcswhich].divisor,
440 				    shellparm[shelltype].inf,
441 				    shellparm[shelltype].lprm[rcswhich].pfx,
442 				    shellparm[shelltype].lprm[rcswhich].sfx,
443 				    shellparm[shelltype].soft);
444 		    }
445 		}
446 	    }
447 	}
448     }
449 
450     login_close(lc);
451     exit(EXIT_SUCCESS);
452 }
453 
454 
455 static void
456 usage(void)
457 {
458     (void)fprintf(stderr,
459 "usage: limits [-C class|-U user] [-eaSHBE] [-bcdflmnstu [val]] [[name=val ...] cmd]\n");
460     exit(EXIT_FAILURE);
461 }
462 
463 static void
464 print_limit(rlim_t limit, unsigned divisor, const char * inf, const char * pfx, const char * sfx, const char * which)
465 {
466     char numbr[64];
467 
468     if (limit == RLIM_INFINITY)
469 	strcpy(numbr, inf);
470     else
471 	sprintf(numbr, "%qd", (quad_t)((limit + divisor/2) / divisor));
472     printf(pfx, which, numbr);
473     printf(sfx, which);
474 
475 }
476 
477 
478 static rlim_t
479 resource_num(int which, int ch, const char *str)
480 {
481     rlim_t res = RLIM_INFINITY;
482 
483     if (str != NULL &&
484 	!(strcasecmp(str, "inf") == 0 ||
485 	  strcasecmp(str, "infinity") == 0 ||
486 	  strcasecmp(str, "unlimit") == 0 ||
487 	  strcasecmp(str, "unlimited") == 0)) {
488 	const char * s = str;
489 	char *e;
490 
491 	switch (which) {
492 	case RLIMIT_CPU:	/* time values */
493 	    errno = 0;
494 	    res = 0;
495 	    while (*s) {
496 		rlim_t tim = strtoq(s, &e, 0);
497 		if (e == NULL || e == s || errno)
498 		    break;
499 		switch (*e++) {
500 		case 0:		   	/* end of string */
501 		    e--;
502 		default:
503 		case 's': case 'S':	/* seconds */
504 		    break;
505 		case 'm': case 'M':	/* minutes */
506 		    tim *= 60L;
507 		    break;
508 		case 'h': case 'H':	/* hours */
509 		    tim *= (60L * 60L);
510 		    break;
511 		case 'd': case 'D':	/* days */
512 		    tim *= (60L * 60L * 24L);
513 		    break;
514 		case 'w': case 'W':	/* weeks */
515 		    tim *= (60L * 60L * 24L * 7L);
516 		case 'y': case 'Y':	/* Years */
517 		    tim *= (60L * 60L * 24L * 365L);
518 		}
519 		s = e;
520 		res += tim;
521 	    }
522 	    break;
523 	case RLIMIT_FSIZE: /* Size values */
524 	case RLIMIT_DATA:
525 	case RLIMIT_STACK:
526 	case RLIMIT_CORE:
527 	case RLIMIT_RSS:
528 	case RLIMIT_MEMLOCK:
529 	    errno = 0;
530 	    res = 0;
531 	    while (*s) {
532 		rlim_t mult, tim = strtoq(s, &e, 0);
533 		if (e == NULL || e == s || errno)
534 		    break;
535 		switch (*e++) {
536 		case 0:	/* end of string */
537 		    e--;
538 		default:
539 		    mult = 1;
540 		    break;
541 		case 'b': case 'B':	/* 512-byte blocks */
542 		    mult = 512;
543 		    break;
544 		case 'k': case 'K':	/* 1024-byte Kilobytes */
545 		    mult = 1024;
546 		    break;
547 		case 'm': case 'M':	/* 1024-k kbytes */
548 		    mult = 1024 * 1024;
549 		    break;
550 		case 'g': case 'G':	/* 1Gbyte */
551 		    mult = 1024 * 1024 * 1024;
552 		    break;
553 		case 't': case 'T':	/* 1TBte */
554 		    mult = 1024LL * 1024LL * 1024LL * 1024LL;
555 		    break;
556 		}
557 		s = e;
558 		res += (tim * mult);
559 	    }
560 	    break;
561 	case RLIMIT_NPROC:
562 	case RLIMIT_NOFILE:
563 	    res = strtoq(s, &e, 0);
564 	    s = e;
565 	    break;
566 	}
567 	if (*s) {
568 	    warnx("invalid value -%c `%s'", ch, str);
569 	    usage();
570 	}
571     }
572     return res;
573 }
574 
575 
576 static int
577 getshellbyname(const char * shell)
578 {
579     int i;
580     const char * q;
581     const char * p = strrchr(shell, '/');
582 
583     p = p ? ++p : shell;
584     for (i = 0; (q = shellparm[i].name) != NULL; i++) {
585 	while (*q) {
586 	    int j = strcspn(q, "|");
587 
588 	    if (j == 0)
589 		break;
590 	    if (strncmp(p, q, j) == 0)
591 		return i;
592 	    if (*(q += j))
593 		++q;
594 	}
595     }
596     return SH_SH;
597 }
598 
599 
600 /*
601  * Determine the type of shell our parent process is
602  * This is quite tricky, not 100% reliable and probably
603  * not nearly as thorough as it should be. Basically, this
604  * is a "best guess" only, but hopefully will work in
605  * most cases.
606  */
607 
608 static int
609 getshelltype(void)
610 {
611     pid_t ppid = getppid();
612 
613     if (ppid != 1) {
614 	FILE * fp;
615 	struct stat st;
616 	char procdir[MAXPATHLEN], buf[128];
617 	int l = sprintf(procdir, "/proc/%ld/", (long)ppid);
618 	char * shell = getenv("SHELL");
619 
620 	if (shell != NULL && stat(shell, &st) != -1) {
621 	    struct stat st1;
622 
623 	    strcpy(procdir+l, "file");
624 	    /* $SHELL is actual shell? */
625 	    if (stat(procdir, &st1) != -1 && memcmp(&st, &st1, sizeof st) == 0)
626 		return getshellbyname(shell);
627 	}
628 	strcpy(procdir+l, "status");
629 	if (stat(procdir, &st) == 0 && (fp = fopen(procdir, "r")) != NULL) {
630 	    char * p = fgets(buf, sizeof buf, fp)==NULL ? NULL : strtok(buf, " \t");
631 	    fclose(fp);
632 	    if (p != NULL)
633 		return getshellbyname(p);
634 	}
635     }
636     return SH_SH;
637 }
638 
639