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