src/basic/fileio.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <ctype.h>
   4 #include <errno.h>
   5 #include <fcntl.h>
   6 #include <limits.h>
   7 #include <stdarg.h>
   8 #include <stdint.h>
   9 #include <stdio_ext.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <sys/stat.h>
  13 #include <sys/types.h>
  14 #include <unistd.h>
  15
  16 #include "alloc-util.h"
  17 #include "fd-util.h"
  18 #include "fileio.h"
  19 #include "fs-util.h"
  20 #include "hexdecoct.h"
  21 #include "log.h"
  22 #include "macro.h"
  23 #include "missing.h"
  24 #include "parse-util.h"
  25 #include "path-util.h"
  26 #include "stdio-util.h"
  27 #include "string-util.h"
  28 #include "tmpfile-util.h"
  29
  30 #define READ_FULL_BYTES_MAX (4U*1024U*1024U)
  31
  32 int fopen_unlocked(const char *path, const char *options, FILE **ret) {
  33         assert(ret);
  34
  35         FILE *f = fopen(path, options);
  36         if (!f)
  37                 return -errno;
  38
  39         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
  40
  41         *ret = f;
  42         return 0;
  43 }
  44
  45 int write_string_stream_ts(
  46                 FILE *f,
  47                 const char *line,
  48                 WriteStringFileFlags flags,
  49                 struct timespec *ts) {
  50
  51         bool needs_nl;
  52         int r;
  53
  54         assert(f);
  55         assert(line);
  56
  57         if (ferror(f))
  58                 return -EIO;
  59
  60         needs_nl = !(flags & WRITE_STRING_FILE_AVOID_NEWLINE) && !endswith(line, "\n");
  61
  62         if (needs_nl && (flags & WRITE_STRING_FILE_DISABLE_BUFFER)) {
  63                 /* If STDIO buffering was disabled, then let's append the newline character to the string itself, so
  64                  * that the write goes out in one go, instead of two */
  65
  66                 line = strjoina(line, "\n");
  67                 needs_nl = false;
  68         }
  69
  70         if (fputs(line, f) == EOF)
  71                 return -errno;
  72
  73         if (needs_nl)
  74                 if (fputc('\n', f) == EOF)
  75                         return -errno;
  76
  77         if (flags & WRITE_STRING_FILE_SYNC)
  78                 r = fflush_sync_and_check(f);
  79         else
  80                 r = fflush_and_check(f);
  81         if (r < 0)
  82                 return r;
  83
  84         if (ts) {
  85                 struct timespec twice[2] = {*ts, *ts};
  86
  87                 if (futimens(fileno(f), twice) < 0)
  88                         return -errno;
  89         }
  90
  91         return 0;
  92 }
  93
  94 static int write_string_file_atomic(
  95                 const char *fn,
  96                 const char *line,
  97                 WriteStringFileFlags flags,
  98                 struct timespec *ts) {
  99
 100         _cleanup_fclose_ FILE *f = NULL;
 101         _cleanup_free_ char *p = NULL;
 102         int r;
 103
 104         assert(fn);
 105         assert(line);
 106
 107         r = fopen_temporary(fn, &f, &p);
 108         if (r < 0)
 109                 return r;
 110
 111         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
 112         (void) fchmod_umask(fileno(f), 0644);
 113
 114         r = write_string_stream_ts(f, line, flags, ts);
 115         if (r < 0)
 116                 goto fail;
 117
 118         if (rename(p, fn) < 0) {
 119                 r = -errno;
 120                 goto fail;
 121         }
 122
 123         return 0;
 124
 125 fail:
 126         (void) unlink(p);
 127         return r;
 128 }
 129
 130 int write_string_file_ts(
 131                 const char *fn,
 132                 const char *line,
 133                 WriteStringFileFlags flags,
 134                 struct timespec *ts) {
 135
 136         _cleanup_fclose_ FILE *f = NULL;
 137         int q, r;
 138
 139         assert(fn);
 140         assert(line);
 141
 142         /* We don't know how to verify whether the file contents was already on-disk. */
 143         assert(!((flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE) && (flags & WRITE_STRING_FILE_SYNC)));
 144
 145         if (flags & WRITE_STRING_FILE_ATOMIC) {
 146                 assert(flags & WRITE_STRING_FILE_CREATE);
 147
 148                 r = write_string_file_atomic(fn, line, flags, ts);
 149                 if (r < 0)
 150                         goto fail;
 151
 152                 return r;
 153         } else
 154                 assert(!ts);
 155
 156         if (flags & WRITE_STRING_FILE_CREATE) {
 157                 f = fopen(fn, "we");
 158                 if (!f) {
 159                         r = -errno;
 160                         goto fail;
 161                 }
 162         } else {
 163                 int fd;
 164
 165                 /* We manually build our own version of fopen(..., "we") that
 166                  * works without O_CREAT */
 167                 fd = open(fn, O_WRONLY|O_CLOEXEC|O_NOCTTY | ((flags & WRITE_STRING_FILE_NOFOLLOW) ? O_NOFOLLOW : 0));
 168                 if (fd < 0) {
 169                         r = -errno;
 170                         goto fail;
 171                 }
 172
 173                 f = fdopen(fd, "w");
 174                 if (!f) {
 175                         r = -errno;
 176                         safe_close(fd);
 177                         goto fail;
 178                 }
 179         }
 180
 181         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
 182
 183         if (flags & WRITE_STRING_FILE_DISABLE_BUFFER)
 184                 setvbuf(f, NULL, _IONBF, 0);
 185
 186         r = write_string_stream_ts(f, line, flags, ts);
 187         if (r < 0)
 188                 goto fail;
 189
 190         return 0;
 191
 192 fail:
 193         if (!(flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE))
 194                 return r;
 195
 196         f = safe_fclose(f);
 197
 198         /* OK, the operation failed, but let's see if the right
 199          * contents in place already. If so, eat up the error. */
 200
 201         q = verify_file(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE));
 202         if (q <= 0)
 203                 return r;
 204
 205         return 0;
 206 }
 207
 208 int write_string_filef(
 209                 const char *fn,
 210                 WriteStringFileFlags flags,
 211                 const char *format, ...) {
 212
 213         _cleanup_free_ char *p = NULL;
 214         va_list ap;
 215         int r;
 216
 217         va_start(ap, format);
 218         r = vasprintf(&p, format, ap);
 219         va_end(ap);
 220
 221         if (r < 0)
 222                 return -ENOMEM;
 223
 224         return write_string_file(fn, p, flags);
 225 }
 226
 227 int read_one_line_file(const char *fn, char **line) {
 228         _cleanup_fclose_ FILE *f = NULL;
 229         int r;
 230
 231         assert(fn);
 232         assert(line);
 233
 234         r = fopen_unlocked(fn, "re", &f);
 235         if (r < 0)
 236                 return r;
 237
 238         return read_line(f, LONG_LINE_MAX, line);
 239 }
 240
 241 int verify_file(const char *fn, const char *blob, bool accept_extra_nl) {
 242         _cleanup_fclose_ FILE *f = NULL;
 243         _cleanup_free_ char *buf = NULL;
 244         size_t l, k;
 245         int r;
 246
 247         assert(fn);
 248         assert(blob);
 249
 250         l = strlen(blob);
 251
 252         if (accept_extra_nl && endswith(blob, "\n"))
 253                 accept_extra_nl = false;
 254
 255         buf = malloc(l + accept_extra_nl + 1);
 256         if (!buf)
 257                 return -ENOMEM;
 258
 259         r = fopen_unlocked(fn, "re", &f);
 260         if (r < 0)
 261                 return r;
 262
 263         /* We try to read one byte more than we need, so that we know whether we hit eof */
 264         errno = 0;
 265         k = fread(buf, 1, l + accept_extra_nl + 1, f);
 266         if (ferror(f))
 267                 return errno > 0 ? -errno : -EIO;
 268
 269         if (k != l && k != l + accept_extra_nl)
 270                 return 0;
 271         if (memcmp(buf, blob, l) != 0)
 272                 return 0;
 273         if (k > l && buf[l] != '\n')
 274                 return 0;
 275
 276         return 1;
 277 }
 278
 279 int read_full_stream_full(
 280                 FILE *f,
 281                 const char *filename,
 282                 ReadFullFileFlags flags,
 283                 char **ret_contents,
 284                 size_t *ret_size) {
 285
 286         _cleanup_free_ char *buf = NULL;
 287         struct stat st;
 288         size_t n, n_next, l;
 289         int fd, r;
 290
 291         assert(f);
 292         assert(ret_contents);
 293         assert(!(flags & READ_FULL_FILE_UNBASE64) || ret_size);
 294
 295         n_next = LINE_MAX; /* Start size */
 296
 297         fd = fileno(f);
 298         if (fd >= 0) { /* If the FILE* object is backed by an fd (as opposed to memory or such, see fmemopen(), let's
 299                         * optimize our buffering) */
 300
 301                 if (fstat(fd, &st) < 0)
 302                         return -errno;
 303
 304                 if (S_ISREG(st.st_mode)) {
 305
 306                         /* Safety check */
 307                         if (st.st_size > READ_FULL_BYTES_MAX)
 308                                 return -E2BIG;
 309
 310                         /* Start with the right file size, but be prepared for files from /proc which generally report a file
 311                          * size of 0. Note that we increase the size to read here by one, so that the first read attempt
 312                          * already makes us notice the EOF. */
 313                         if (st.st_size > 0)
 314                                 n_next = st.st_size + 1;
 315
 316                         if (flags & READ_FULL_FILE_SECURE)
 317                                 (void) warn_file_is_world_accessible(filename, &st, NULL, 0);
 318                 }
 319         }
 320
 321         n = l = 0;
 322         for (;;) {
 323                 char *t;
 324                 size_t k;
 325
 326                 if (flags & READ_FULL_FILE_SECURE) {
 327                         t = malloc(n_next + 1);
 328                         if (!t) {
 329                                 r = -ENOMEM;
 330                                 goto finalize;
 331                         }
 332                         memcpy_safe(t, buf, n);
 333                         explicit_bzero_safe(buf, n);
 334                 } else {
 335                         t = realloc(buf, n_next + 1);
 336                         if (!t)
 337                                 return -ENOMEM;
 338                 }
 339
 340                 buf = t;
 341                 n = n_next;
 342
 343                 errno = 0;
 344                 k = fread(buf + l, 1, n - l, f);
 345                 if (k > 0)
 346                         l += k;
 347
 348                 if (ferror(f)) {
 349                         r = errno > 0 ? -errno : -EIO;
 350                         goto finalize;
 351                 }
 352
 353                 if (feof(f))
 354                         break;
 355
 356                 /* We aren't expecting fread() to return a short read outside
 357                  * of (error && eof), assert buffer is full and enlarge buffer.
 358                  */
 359                 assert(l == n);
 360
 361                 /* Safety check */
 362                 if (n >= READ_FULL_BYTES_MAX) {
 363                         r = -E2BIG;
 364                         goto finalize;
 365                 }
 366
 367                 n_next = MIN(n * 2, READ_FULL_BYTES_MAX);
 368         }
 369
 370         if (flags & READ_FULL_FILE_UNBASE64) {
 371                 buf[l++] = 0;
 372                 r = unbase64mem_full(buf, l, flags & READ_FULL_FILE_SECURE, (void **) ret_contents, ret_size);
 373                 goto finalize;
 374         }
 375
 376         if (!ret_size) {
 377                 /* Safety check: if the caller doesn't want to know the size of what we just read it will rely on the
 378                  * trailing NUL byte. But if there's an embedded NUL byte, then we should refuse operation as otherwise
 379                  * there'd be ambiguity about what we just read. */
 380
 381                 if (memchr(buf, 0, l)) {
 382                         r = -EBADMSG;
 383                         goto finalize;
 384                 }
 385         }
 386
 387         buf[l] = 0;
 388         *ret_contents = TAKE_PTR(buf);
 389
 390         if (ret_size)
 391                 *ret_size = l;
 392
 393         return 0;
 394
 395 finalize:
 396         if (flags & READ_FULL_FILE_SECURE)
 397                 explicit_bzero_safe(buf, n);
 398
 399         return r;
 400 }
 401
 402 int read_full_file_full(const char *filename, ReadFullFileFlags flags, char **contents, size_t *size) {
 403         _cleanup_fclose_ FILE *f = NULL;
 404         int r;
 405
 406         assert(filename);
 407         assert(contents);
 408
 409         r = fopen_unlocked(filename, "re", &f);
 410         if (r < 0)
 411                 return r;
 412
 413         return read_full_stream_full(f, filename, flags, contents, size);
 414 }
 415
 416 int executable_is_script(const char *path, char **interpreter) {
 417         _cleanup_free_ char *line = NULL;
 418         size_t len;
 419         char *ans;
 420         int r;
 421
 422         assert(path);
 423
 424         r = read_one_line_file(path, &line);
 425         if (r == -ENOBUFS) /* First line overly long? if so, then it's not a script */
 426                 return 0;
 427         if (r < 0)
 428                 return r;
 429
 430         if (!startswith(line, "#!"))
 431                 return 0;
 432
 433         ans = strstrip(line + 2);
 434         len = strcspn(ans, " \t");
 435
 436         if (len == 0)
 437                 return 0;
 438
 439         ans = strndup(ans, len);
 440         if (!ans)
 441                 return -ENOMEM;
 442
 443         *interpreter = ans;
 444         return 1;
 445 }
 446
 447 /**
 448  * Retrieve one field from a file like /proc/self/status.  pattern
 449  * should not include whitespace or the delimiter (':'). pattern matches only
 450  * the beginning of a line. Whitespace before ':' is skipped. Whitespace and
 451  * zeros after the ':' will be skipped. field must be freed afterwards.
 452  * terminator specifies the terminating characters of the field value (not
 453  * included in the value).
 454  */
 455 int get_proc_field(const char *filename, const char *pattern, const char *terminator, char **field) {
 456         _cleanup_free_ char *status = NULL;
 457         char *t, *f;
 458         size_t len;
 459         int r;
 460
 461         assert(terminator);
 462         assert(filename);
 463         assert(pattern);
 464         assert(field);
 465
 466         r = read_full_file(filename, &status, NULL);
 467         if (r < 0)
 468                 return r;
 469
 470         t = status;
 471
 472         do {
 473                 bool pattern_ok;
 474
 475                 do {
 476                         t = strstr(t, pattern);
 477                         if (!t)
 478                                 return -ENOENT;
 479
 480                         /* Check that pattern occurs in beginning of line. */
 481                         pattern_ok = (t == status || t[-1] == '\n');
 482
 483                         t += strlen(pattern);
 484
 485                 } while (!pattern_ok);
 486
 487                 t += strspn(t, " \t");
 488                 if (!*t)
 489                         return -ENOENT;
 490
 491         } while (*t != ':');
 492
 493         t++;
 494
 495         if (*t) {
 496                 t += strspn(t, " \t");
 497
 498                 /* Also skip zeros, because when this is used for
 499                  * capabilities, we don't want the zeros. This way the
 500                  * same capability set always maps to the same string,
 501                  * irrespective of the total capability set size. For
 502                  * other numbers it shouldn't matter. */
 503                 t += strspn(t, "0");
 504                 /* Back off one char if there's nothing but whitespace
 505                    and zeros */
 506                 if (!*t || isspace(*t))
 507                         t--;
 508         }
 509
 510         len = strcspn(t, terminator);
 511
 512         f = strndup(t, len);
 513         if (!f)
 514                 return -ENOMEM;
 515
 516         *field = f;
 517         return 0;
 518 }
 519
 520 DIR *xopendirat(int fd, const char *name, int flags) {
 521         int nfd;
 522         DIR *d;
 523
 524         assert(!(flags & O_CREAT));
 525
 526         nfd = openat(fd, name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|flags, 0);
 527         if (nfd < 0)
 528                 return NULL;
 529
 530         d = fdopendir(nfd);
 531         if (!d) {
 532                 safe_close(nfd);
 533                 return NULL;
 534         }
 535
 536         return d;
 537 }
 538
 539 static int search_and_fopen_internal(const char *path, const char *mode, const char *root, char **search, FILE **_f) {
 540         char **i;
 541
 542         assert(path);
 543         assert(mode);
 544         assert(_f);
 545
 546         if (!path_strv_resolve_uniq(search, root))
 547                 return -ENOMEM;
 548
 549         STRV_FOREACH(i, search) {
 550                 _cleanup_free_ char *p = NULL;
 551                 FILE *f;
 552
 553                 if (root)
 554                         p = strjoin(root, *i, "/", path);
 555                 else
 556                         p = strjoin(*i, "/", path);
 557                 if (!p)
 558                         return -ENOMEM;
 559
 560                 f = fopen(p, mode);
 561                 if (f) {
 562                         *_f = f;
 563                         return 0;
 564                 }
 565
 566                 if (errno != ENOENT)
 567                         return -errno;
 568         }
 569
 570         return -ENOENT;
 571 }
 572
 573 int search_and_fopen(const char *path, const char *mode, const char *root, const char **search, FILE **_f) {
 574         _cleanup_strv_free_ char **copy = NULL;
 575
 576         assert(path);
 577         assert(mode);
 578         assert(_f);
 579
 580         if (path_is_absolute(path)) {
 581                 FILE *f;
 582
 583                 f = fopen(path, mode);
 584                 if (f) {
 585                         *_f = f;
 586                         return 0;
 587                 }
 588
 589                 return -errno;
 590         }
 591
 592         copy = strv_copy((char**) search);
 593         if (!copy)
 594                 return -ENOMEM;
 595
 596         return search_and_fopen_internal(path, mode, root, copy, _f);
 597 }
 598
 599 int search_and_fopen_nulstr(const char *path, const char *mode, const char *root, const char *search, FILE **_f) {
 600         _cleanup_strv_free_ char **s = NULL;
 601
 602         if (path_is_absolute(path)) {
 603                 FILE *f;
 604
 605                 f = fopen(path, mode);
 606                 if (f) {
 607                         *_f = f;
 608                         return 0;
 609                 }
 610
 611                 return -errno;
 612         }
 613
 614         s = strv_split_nulstr(search);
 615         if (!s)
 616                 return -ENOMEM;
 617
 618         return search_and_fopen_internal(path, mode, root, s, _f);
 619 }
 620
 621 int fflush_and_check(FILE *f) {
 622         assert(f);
 623
 624         errno = 0;
 625         fflush(f);
 626
 627         if (ferror(f))
 628                 return errno > 0 ? -errno : -EIO;
 629
 630         return 0;
 631 }
 632
 633 int fflush_sync_and_check(FILE *f) {
 634         int r;
 635
 636         assert(f);
 637
 638         r = fflush_and_check(f);
 639         if (r < 0)
 640                 return r;
 641
 642         if (fsync(fileno(f)) < 0)
 643                 return -errno;
 644
 645         r = fsync_directory_of_file(fileno(f));
 646         if (r < 0)
 647                 return r;
 648
 649         return 0;
 650 }
 651
 652 int write_timestamp_file_atomic(const char *fn, usec_t n) {
 653         char ln[DECIMAL_STR_MAX(n)+2];
 654
 655         /* Creates a "timestamp" file, that contains nothing but a
 656          * usec_t timestamp, formatted in ASCII. */
 657
 658         if (n <= 0 || n >= USEC_INFINITY)
 659                 return -ERANGE;
 660
 661         xsprintf(ln, USEC_FMT "\n", n);
 662
 663         return write_string_file(fn, ln, WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_ATOMIC);
 664 }
 665
 666 int read_timestamp_file(const char *fn, usec_t *ret) {
 667         _cleanup_free_ char *ln = NULL;
 668         uint64_t t;
 669         int r;
 670
 671         r = read_one_line_file(fn, &ln);
 672         if (r < 0)
 673                 return r;
 674
 675         r = safe_atou64(ln, &t);
 676         if (r < 0)
 677                 return r;
 678
 679         if (t <= 0 || t >= (uint64_t) USEC_INFINITY)
 680                 return -ERANGE;
 681
 682         *ret = (usec_t) t;
 683         return 0;
 684 }
 685
 686 int fputs_with_space(FILE *f, const char *s, const char *separator, bool *space) {
 687         int r;
 688
 689         assert(s);
 690
 691         /* Outputs the specified string with fputs(), but optionally prefixes it with a separator. The *space parameter
 692          * when specified shall initially point to a boolean variable initialized to false. It is set to true after the
 693          * first invocation. This call is supposed to be use in loops, where a separator shall be inserted between each
 694          * element, but not before the first one. */
 695
 696         if (!f)
 697                 f = stdout;
 698
 699         if (space) {
 700                 if (!separator)
 701                         separator = " ";
 702
 703                 if (*space) {
 704                         r = fputs(separator, f);
 705                         if (r < 0)
 706                                 return r;
 707                 }
 708
 709                 *space = true;
 710         }
 711
 712         return fputs(s, f);
 713 }
 714
 715 /* A bitmask of the EOL markers we know */
 716 typedef enum EndOfLineMarker {
 717         EOL_NONE     = 0,
 718         EOL_ZERO     = 1 << 0,  /* \0 (aka NUL) */
 719         EOL_TEN      = 1 << 1,  /* \n (aka NL, aka LF)  */
 720         EOL_THIRTEEN = 1 << 2,  /* \r (aka CR)  */
 721 } EndOfLineMarker;
 722
 723 static EndOfLineMarker categorize_eol(char c, ReadLineFlags flags) {
 724
 725         if (!IN_SET(flags, READ_LINE_ONLY_NUL)) {
 726                 if (c == '\n')
 727                         return EOL_TEN;
 728                 if (c == '\r')
 729                         return EOL_THIRTEEN;
 730         }
 731
 732         if (c == '\0')
 733                 return EOL_ZERO;
 734
 735         return EOL_NONE;
 736 }
 737
 738 DEFINE_TRIVIAL_CLEANUP_FUNC(FILE*, funlockfile);
 739
 740 int read_line_full(FILE *f, size_t limit, ReadLineFlags flags, char **ret) {
 741         size_t n = 0, allocated = 0, count = 0;
 742         _cleanup_free_ char *buffer = NULL;
 743         int r;
 744
 745         assert(f);
 746
 747         /* Something like a bounded version of getline().
 748          *
 749          * Considers EOF, \n, \r and \0 end of line delimiters (or combinations of these), and does not include these
 750          * delimiters in the string returned. Specifically, recognizes the following combinations of markers as line
 751          * endings:
 752          *
 753          *     • \n        (UNIX)
 754          *     • \r        (old MacOS)
 755          *     • \0        (C strings)
 756          *     • \n\0
 757          *     • \r\0
 758          *     • \r\n      (Windows)
 759          *     • \n\r
 760          *     • \r\n\0
 761          *     • \n\r\0
 762          *
 763          * Returns the number of bytes read from the files (i.e. including delimiters — this hence usually differs from
 764          * the number of characters in the returned string). When EOF is hit, 0 is returned.
 765          *
 766          * The input parameter limit is the maximum numbers of characters in the returned string, i.e. excluding
 767          * delimiters. If the limit is hit we fail and return -ENOBUFS.
 768          *
 769          * If a line shall be skipped ret may be initialized as NULL. */
 770
 771         if (ret) {
 772                 if (!GREEDY_REALLOC(buffer, allocated, 1))
 773                         return -ENOMEM;
 774         }
 775
 776         {
 777                 _unused_ _cleanup_(funlockfilep) FILE *flocked = f;
 778                 EndOfLineMarker previous_eol = EOL_NONE;
 779                 flockfile(f);
 780
 781                 for (;;) {
 782                         EndOfLineMarker eol;
 783                         char c;
 784
 785                         if (n >= limit)
 786                                 return -ENOBUFS;
 787
 788                         if (count >= INT_MAX) /* We couldn't return the counter anymore as "int", hence refuse this */
 789                                 return -ENOBUFS;
 790
 791                         r = safe_fgetc(f, &c);
 792                         if (r < 0)
 793                                 return r;
 794                         if (r == 0) /* EOF is definitely EOL */
 795                                 break;
 796
 797                         eol = categorize_eol(c, flags);
 798
 799                         if (FLAGS_SET(previous_eol, EOL_ZERO) ||
 800                             (eol == EOL_NONE && previous_eol != EOL_NONE) ||
 801                             (eol != EOL_NONE && (previous_eol & eol) != 0)) {
 802                                 /* Previous char was a NUL? This is not an EOL, but the previous char was? This type of
 803                                  * EOL marker has been seen right before?  In either of these three cases we are
 804                                  * done. But first, let's put this character back in the queue. (Note that we have to
 805                                  * cast this to (unsigned char) here as ungetc() expects a positive 'int', and if we
 806                                  * are on an architecture where 'char' equals 'signed char' we need to ensure we don't
 807                                  * pass a negative value here. That said, to complicate things further ungetc() is
 808                                  * actually happy with most negative characters and implicitly casts them back to
 809                                  * positive ones as needed, except for \xff (aka -1, aka EOF), which it refuses. What a
 810                                  * godawful API!) */
 811                                 assert_se(ungetc((unsigned char) c, f) != EOF);
 812                                 break;
 813                         }
 814
 815                         count++;
 816
 817                         if (eol != EOL_NONE) {
 818                                 previous_eol |= eol;
 819                                 continue;
 820                         }
 821
 822                         if (ret) {
 823                                 if (!GREEDY_REALLOC(buffer, allocated, n + 2))
 824                                         return -ENOMEM;
 825
 826                                 buffer[n] = c;
 827                         }
 828
 829                         n++;
 830                 }
 831         }
 832
 833         if (ret) {
 834                 buffer[n] = 0;
 835
 836                 *ret = TAKE_PTR(buffer);
 837         }
 838
 839         return (int) count;
 840 }
 841
 842 int safe_fgetc(FILE *f, char *ret) {
 843         int k;
 844
 845         assert(f);
 846
 847         /* A safer version of plain fgetc(): let's propagate the error that happened while reading as such, and
 848          * separate the EOF condition from the byte read, to avoid those confusion signed/unsigned issues fgetc()
 849          * has. */
 850
 851         errno = 0;
 852         k = fgetc(f);
 853         if (k == EOF) {
 854                 if (ferror(f))
 855                         return errno > 0 ? -errno : -EIO;
 856
 857                 if (ret)
 858                         *ret = 0;
 859
 860                 return 0;
 861         }
 862
 863         if (ret)
 864                 *ret = k;
 865
 866         return 1;
 867 }
 868
 869 int warn_file_is_world_accessible(const char *filename, struct stat *st, const char *unit, unsigned line) {
 870         struct stat _st;
 871
 872         if (!filename)
 873                 return 0;
 874
 875         if (!st) {
 876                 if (stat(filename, &_st) < 0)
 877                         return -errno;
 878                 st = &_st;
 879         }
 880
 881         if ((st->st_mode & S_IRWXO) == 0)
 882                 return 0;
 883
 884         if (unit)
 885                 log_syntax(unit, LOG_WARNING, filename, line, 0,
 886                            "%s has %04o mode that is too permissive, please adjust the access mode.",
 887                            filename, st->st_mode & 07777);
 888         else
 889                 log_warning("%s has %04o mode that is too permissive, please adjust the access mode.",
 890                             filename, st->st_mode & 07777);
 891         return 0;
 892 }