Eric Andersen | abc0f4f | 1999-12-08 23:19:36 +0000 | [diff] [blame^] | 1 | /* tail -- output the last part of file(s) |
| 2 | Copyright (C) 89, 90, 91, 95, 1996 Free Software Foundation, Inc. |
| 3 | |
| 4 | This program is free software; you can redistribute it and/or modify |
| 5 | it under the terms of the GNU General Public License as published by |
| 6 | the Free Software Foundation; either version 2, or (at your option) |
| 7 | any later version. |
| 8 | |
| 9 | This program is distributed in the hope that it will be useful, |
| 10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | GNU General Public License for more details. |
| 13 | |
| 14 | You should have received a copy of the GNU General Public License |
| 15 | along with this program; if not, write to the Free Software |
| 16 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ |
| 17 | |
| 18 | /* Can display any amount of data, unlike the Unix version, which uses |
| 19 | a fixed size buffer and therefore can only deliver a limited number |
| 20 | of lines. |
| 21 | |
| 22 | Options: |
| 23 | -b Tail by N 512-byte blocks. |
| 24 | -c, --bytes=N[bkm] Tail by N bytes |
| 25 | [or 512-byte blocks, kilobytes, or megabytes]. |
| 26 | -f, --follow Loop forever trying to read more characters at the |
| 27 | end of the file, on the assumption that the file |
| 28 | is growing. Ignored if reading from a pipe. |
| 29 | -n, --lines=N Tail by N lines. |
| 30 | -q, --quiet, --silent Never print filename headers. |
| 31 | -v, --verbose Always print filename headers. |
| 32 | |
| 33 | If a number (N) starts with a `+', begin printing with the Nth item |
| 34 | from the start of each file, instead of from the end. |
| 35 | |
| 36 | Reads from standard input if no files are given or when a filename of |
| 37 | ``-'' is encountered. |
| 38 | By default, filename headers are printed only more than one file |
| 39 | is given. |
| 40 | By default, prints the last 10 lines (tail -n 10). |
| 41 | |
| 42 | Original version by Paul Rubin <phr@ocf.berkeley.edu>. |
| 43 | Extensions by David MacKenzie <djm@gnu.ai.mit.edu>. |
| 44 | tail -f for multiple files by Ian Lance Taylor <ian@airs.com>. */ |
| 45 | |
| 46 | #include "internal.h" |
| 47 | |
| 48 | #include <stdio.h> |
| 49 | #include <assert.h> |
| 50 | #include <errno.h> |
| 51 | #include <sys/types.h> |
| 52 | |
| 53 | |
| 54 | /* Disable assertions. Some systems have broken assert macros. */ |
| 55 | #define NDEBUG 1 |
| 56 | |
| 57 | |
| 58 | static void error(int i, int errnum, char* fmt, const char *msg) |
| 59 | { |
| 60 | fprintf(stderr, fmt, msg); |
| 61 | perror( errnum); |
| 62 | exit(i); |
| 63 | } |
| 64 | |
| 65 | |
| 66 | #define XWRITE(fd, buffer, n_bytes) \ |
| 67 | do \ |
| 68 | { \ |
| 69 | assert ((fd) == 1); \ |
| 70 | assert ((n_bytes) >= 0); \ |
| 71 | if (n_bytes > 0 && fwrite ((buffer), 1, (n_bytes), stdout) == 0) \ |
| 72 | error (EXIT_FAILURE, errno, "write error", NULL); \ |
| 73 | } \ |
| 74 | while (0) |
| 75 | |
| 76 | /* Number of items to tail. */ |
| 77 | #define DEFAULT_N_LINES 10 |
| 78 | |
| 79 | /* Size of atomic reads. */ |
| 80 | #ifndef BUFSIZ |
| 81 | #define BUFSIZ (512 * 8) |
| 82 | #endif |
| 83 | |
| 84 | /* If nonzero, interpret the numeric argument as the number of lines. |
| 85 | Otherwise, interpret it as the number of bytes. */ |
| 86 | static int count_lines; |
| 87 | |
| 88 | /* If nonzero, read from the end of one file until killed. */ |
| 89 | static int forever; |
| 90 | |
| 91 | /* If nonzero, read from the end of multiple files until killed. */ |
| 92 | static int forever_multiple; |
| 93 | |
| 94 | /* Array of file descriptors if forever_multiple is 1. */ |
| 95 | static int *file_descs; |
| 96 | |
| 97 | /* Array of file sizes if forever_multiple is 1. */ |
| 98 | static off_t *file_sizes; |
| 99 | |
| 100 | /* If nonzero, count from start of file instead of end. */ |
| 101 | static int from_start; |
| 102 | |
| 103 | /* If nonzero, print filename headers. */ |
| 104 | static int print_headers; |
| 105 | |
| 106 | /* When to print the filename banners. */ |
| 107 | enum header_mode |
| 108 | { |
| 109 | multiple_files, always, never |
| 110 | }; |
| 111 | |
| 112 | char *xmalloc (); |
| 113 | int safe_read (); |
| 114 | |
| 115 | /* The name this program was run with. */ |
| 116 | char *program_name; |
| 117 | |
| 118 | /* Nonzero if we have ever read standard input. */ |
| 119 | static int have_read_stdin; |
| 120 | |
| 121 | /* If nonzero, display usage information and exit. */ |
| 122 | static int show_help; |
| 123 | |
| 124 | /* If nonzero, print the version on standard output then exit. */ |
| 125 | static int show_version; |
| 126 | |
| 127 | static const char tail_usage[] = |
| 128 | "tail [OPTION]... [FILE]...\n\ |
| 129 | Print last 10 lines of each FILE to standard output.\n\ |
| 130 | With more than one FILE, precede each with a header giving the file name.\n\ |
| 131 | With no FILE, or when FILE is -, read standard input.\n\ |
| 132 | \n\ |
| 133 | -c, --bytes=N output the last N bytes\n\ |
| 134 | -f, --follow output appended data as the file grows\n\ |
| 135 | -n, --lines=N output the last N lines, instead of last 10\n\ |
| 136 | -q, --quiet, --silent never output headers giving file names\n\ |
| 137 | -v, --verbose always output headers giving file names\n\ |
| 138 | --help display this help and exit\n\ |
| 139 | --version output version information and exit\n\ |
| 140 | \n\ |
| 141 | If the first character of N (the number of bytes or lines) is a `+',\n\ |
| 142 | print beginning with the Nth item from the start of each file, otherwise,\n\ |
| 143 | print the last N items in the file. N may have a multiplier suffix:\n\ |
| 144 | b for 512, k for 1024, m for 1048576 (1 Meg). A first OPTION of -VALUE\n\ |
| 145 | or +VALUE is treated like -n VALUE or -n +VALUE unless VALUE has one of\n\ |
| 146 | the [bkm] suffix multipliers, in which case it is treated like -c VALUE\n\ |
| 147 | or -c +VALUE.\n"; |
| 148 | |
| 149 | static void |
| 150 | write_header (const char *filename, const char *comment) |
| 151 | { |
| 152 | static int first_file = 1; |
| 153 | |
| 154 | printf ("%s==> %s%s%s <==\n", (first_file ? "" : "\n"), filename, |
| 155 | (comment ? ": " : ""), |
| 156 | (comment ? comment : "")); |
| 157 | first_file = 0; |
| 158 | } |
| 159 | |
| 160 | /* Print the last N_LINES lines from the end of file FD. |
| 161 | Go backward through the file, reading `BUFSIZ' bytes at a time (except |
| 162 | probably the first), until we hit the start of the file or have |
| 163 | read NUMBER newlines. |
| 164 | POS starts out as the length of the file (the offset of the last |
| 165 | byte of the file + 1). |
| 166 | Return 0 if successful, 1 if an error occurred. */ |
| 167 | |
| 168 | static int |
| 169 | file_lines (const char *filename, int fd, long int n_lines, off_t pos) |
| 170 | { |
| 171 | char buffer[BUFSIZ]; |
| 172 | int bytes_read; |
| 173 | int i; /* Index into `buffer' for scanning. */ |
| 174 | |
| 175 | if (n_lines == 0) |
| 176 | return 0; |
| 177 | |
| 178 | /* Set `bytes_read' to the size of the last, probably partial, buffer; |
| 179 | 0 < `bytes_read' <= `BUFSIZ'. */ |
| 180 | bytes_read = pos % BUFSIZ; |
| 181 | if (bytes_read == 0) |
| 182 | bytes_read = BUFSIZ; |
| 183 | /* Make `pos' a multiple of `BUFSIZ' (0 if the file is short), so that all |
| 184 | reads will be on block boundaries, which might increase efficiency. */ |
| 185 | pos -= bytes_read; |
| 186 | lseek (fd, pos, SEEK_SET); |
| 187 | bytes_read = safe_read (fd, buffer, bytes_read); |
| 188 | if (bytes_read == -1) |
| 189 | { |
| 190 | error (0, errno, "%s", filename); |
| 191 | return 1; |
| 192 | } |
| 193 | |
| 194 | /* Count the incomplete line on files that don't end with a newline. */ |
| 195 | if (bytes_read && buffer[bytes_read - 1] != '\n') |
| 196 | --n_lines; |
| 197 | |
| 198 | do |
| 199 | { |
| 200 | /* Scan backward, counting the newlines in this bufferfull. */ |
| 201 | for (i = bytes_read - 1; i >= 0; i--) |
| 202 | { |
| 203 | /* Have we counted the requested number of newlines yet? */ |
| 204 | if (buffer[i] == '\n' && n_lines-- == 0) |
| 205 | { |
| 206 | /* If this newline wasn't the last character in the buffer, |
| 207 | print the text after it. */ |
| 208 | if (i != bytes_read - 1) |
| 209 | XWRITE (STDOUT_FILENO, &buffer[i + 1], bytes_read - (i + 1)); |
| 210 | return 0; |
| 211 | } |
| 212 | } |
| 213 | /* Not enough newlines in that bufferfull. */ |
| 214 | if (pos == 0) |
| 215 | { |
| 216 | /* Not enough lines in the file; print the entire file. */ |
| 217 | lseek (fd, (off_t) 0, SEEK_SET); |
| 218 | return 0; |
| 219 | } |
| 220 | pos -= BUFSIZ; |
| 221 | lseek (fd, pos, SEEK_SET); |
| 222 | } |
| 223 | while ((bytes_read = safe_read (fd, buffer, BUFSIZ)) > 0); |
| 224 | if (bytes_read == -1) |
| 225 | { |
| 226 | error (0, errno, "%s", filename); |
| 227 | return 1; |
| 228 | } |
| 229 | return 0; |
| 230 | } |
| 231 | |
| 232 | /* Print the last N_LINES lines from the end of the standard input, |
| 233 | open for reading as pipe FD. |
| 234 | Buffer the text as a linked list of LBUFFERs, adding them as needed. |
| 235 | Return 0 if successful, 1 if an error occured. */ |
| 236 | |
| 237 | static int |
| 238 | pipe_lines (const char *filename, int fd, long int n_lines) |
| 239 | { |
| 240 | struct linebuffer |
| 241 | { |
| 242 | int nbytes, nlines; |
| 243 | char buffer[BUFSIZ]; |
| 244 | struct linebuffer *next; |
| 245 | }; |
| 246 | typedef struct linebuffer LBUFFER; |
| 247 | LBUFFER *first, *last, *tmp; |
| 248 | int i; /* Index into buffers. */ |
| 249 | int total_lines = 0; /* Total number of newlines in all buffers. */ |
| 250 | int errors = 0; |
| 251 | |
| 252 | first = last = (LBUFFER *) xmalloc (sizeof (LBUFFER)); |
| 253 | first->nbytes = first->nlines = 0; |
| 254 | first->next = NULL; |
| 255 | tmp = (LBUFFER *) xmalloc (sizeof (LBUFFER)); |
| 256 | |
| 257 | /* Input is always read into a fresh buffer. */ |
| 258 | while ((tmp->nbytes = safe_read (fd, tmp->buffer, BUFSIZ)) > 0) |
| 259 | { |
| 260 | tmp->nlines = 0; |
| 261 | tmp->next = NULL; |
| 262 | |
| 263 | /* Count the number of newlines just read. */ |
| 264 | for (i = 0; i < tmp->nbytes; i++) |
| 265 | if (tmp->buffer[i] == '\n') |
| 266 | ++tmp->nlines; |
| 267 | total_lines += tmp->nlines; |
| 268 | |
| 269 | /* If there is enough room in the last buffer read, just append the new |
| 270 | one to it. This is because when reading from a pipe, `nbytes' can |
| 271 | often be very small. */ |
| 272 | if (tmp->nbytes + last->nbytes < BUFSIZ) |
| 273 | { |
| 274 | memcpy (&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes); |
| 275 | last->nbytes += tmp->nbytes; |
| 276 | last->nlines += tmp->nlines; |
| 277 | } |
| 278 | else |
| 279 | { |
| 280 | /* If there's not enough room, link the new buffer onto the end of |
| 281 | the list, then either free up the oldest buffer for the next |
| 282 | read if that would leave enough lines, or else malloc a new one. |
| 283 | Some compaction mechanism is possible but probably not |
| 284 | worthwhile. */ |
| 285 | last = last->next = tmp; |
| 286 | if (total_lines - first->nlines > n_lines) |
| 287 | { |
| 288 | tmp = first; |
| 289 | total_lines -= first->nlines; |
| 290 | first = first->next; |
| 291 | } |
| 292 | else |
| 293 | tmp = (LBUFFER *) xmalloc (sizeof (LBUFFER)); |
| 294 | } |
| 295 | } |
| 296 | if (tmp->nbytes == -1) |
| 297 | { |
| 298 | error (0, errno, "%s", filename); |
| 299 | errors = 1; |
| 300 | free ((char *) tmp); |
| 301 | goto free_lbuffers; |
| 302 | } |
| 303 | |
| 304 | free ((char *) tmp); |
| 305 | |
| 306 | /* This prevents a core dump when the pipe contains no newlines. */ |
| 307 | if (n_lines == 0) |
| 308 | goto free_lbuffers; |
| 309 | |
| 310 | /* Count the incomplete line on files that don't end with a newline. */ |
| 311 | if (last->buffer[last->nbytes - 1] != '\n') |
| 312 | { |
| 313 | ++last->nlines; |
| 314 | ++total_lines; |
| 315 | } |
| 316 | |
| 317 | /* Run through the list, printing lines. First, skip over unneeded |
| 318 | buffers. */ |
| 319 | for (tmp = first; total_lines - tmp->nlines > n_lines; tmp = tmp->next) |
| 320 | total_lines -= tmp->nlines; |
| 321 | |
| 322 | /* Find the correct beginning, then print the rest of the file. */ |
| 323 | if (total_lines > n_lines) |
| 324 | { |
| 325 | char *cp; |
| 326 | |
| 327 | /* Skip `total_lines' - `n_lines' newlines. We made sure that |
| 328 | `total_lines' - `n_lines' <= `tmp->nlines'. */ |
| 329 | cp = tmp->buffer; |
| 330 | for (i = total_lines - n_lines; i; --i) |
| 331 | while (*cp++ != '\n') |
| 332 | /* Do nothing. */ ; |
| 333 | i = cp - tmp->buffer; |
| 334 | } |
| 335 | else |
| 336 | i = 0; |
| 337 | XWRITE (STDOUT_FILENO, &tmp->buffer[i], tmp->nbytes - i); |
| 338 | |
| 339 | for (tmp = tmp->next; tmp; tmp = tmp->next) |
| 340 | XWRITE (STDOUT_FILENO, tmp->buffer, tmp->nbytes); |
| 341 | |
| 342 | free_lbuffers: |
| 343 | while (first) |
| 344 | { |
| 345 | tmp = first->next; |
| 346 | free ((char *) first); |
| 347 | first = tmp; |
| 348 | } |
| 349 | return errors; |
| 350 | } |
| 351 | |
| 352 | /* Print the last N_BYTES characters from the end of pipe FD. |
| 353 | This is a stripped down version of pipe_lines. |
| 354 | Return 0 if successful, 1 if an error occurred. */ |
| 355 | |
| 356 | static int |
| 357 | pipe_bytes (const char *filename, int fd, off_t n_bytes) |
| 358 | { |
| 359 | struct charbuffer |
| 360 | { |
| 361 | int nbytes; |
| 362 | char buffer[BUFSIZ]; |
| 363 | struct charbuffer *next; |
| 364 | }; |
| 365 | typedef struct charbuffer CBUFFER; |
| 366 | CBUFFER *first, *last, *tmp; |
| 367 | int i; /* Index into buffers. */ |
| 368 | int total_bytes = 0; /* Total characters in all buffers. */ |
| 369 | int errors = 0; |
| 370 | |
| 371 | first = last = (CBUFFER *) xmalloc (sizeof (CBUFFER)); |
| 372 | first->nbytes = 0; |
| 373 | first->next = NULL; |
| 374 | tmp = (CBUFFER *) xmalloc (sizeof (CBUFFER)); |
| 375 | |
| 376 | /* Input is always read into a fresh buffer. */ |
| 377 | while ((tmp->nbytes = safe_read (fd, tmp->buffer, BUFSIZ)) > 0) |
| 378 | { |
| 379 | tmp->next = NULL; |
| 380 | |
| 381 | total_bytes += tmp->nbytes; |
| 382 | /* If there is enough room in the last buffer read, just append the new |
| 383 | one to it. This is because when reading from a pipe, `nbytes' can |
| 384 | often be very small. */ |
| 385 | if (tmp->nbytes + last->nbytes < BUFSIZ) |
| 386 | { |
| 387 | memcpy (&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes); |
| 388 | last->nbytes += tmp->nbytes; |
| 389 | } |
| 390 | else |
| 391 | { |
| 392 | /* If there's not enough room, link the new buffer onto the end of |
| 393 | the list, then either free up the oldest buffer for the next |
| 394 | read if that would leave enough characters, or else malloc a new |
| 395 | one. Some compaction mechanism is possible but probably not |
| 396 | worthwhile. */ |
| 397 | last = last->next = tmp; |
| 398 | if (total_bytes - first->nbytes > n_bytes) |
| 399 | { |
| 400 | tmp = first; |
| 401 | total_bytes -= first->nbytes; |
| 402 | first = first->next; |
| 403 | } |
| 404 | else |
| 405 | { |
| 406 | tmp = (CBUFFER *) xmalloc (sizeof (CBUFFER)); |
| 407 | } |
| 408 | } |
| 409 | } |
| 410 | if (tmp->nbytes == -1) |
| 411 | { |
| 412 | error (0, errno, "%s", filename); |
| 413 | errors = 1; |
| 414 | free ((char *) tmp); |
| 415 | goto free_cbuffers; |
| 416 | } |
| 417 | |
| 418 | free ((char *) tmp); |
| 419 | |
| 420 | /* Run through the list, printing characters. First, skip over unneeded |
| 421 | buffers. */ |
| 422 | for (tmp = first; total_bytes - tmp->nbytes > n_bytes; tmp = tmp->next) |
| 423 | total_bytes -= tmp->nbytes; |
| 424 | |
| 425 | /* Find the correct beginning, then print the rest of the file. |
| 426 | We made sure that `total_bytes' - `n_bytes' <= `tmp->nbytes'. */ |
| 427 | if (total_bytes > n_bytes) |
| 428 | i = total_bytes - n_bytes; |
| 429 | else |
| 430 | i = 0; |
| 431 | XWRITE (STDOUT_FILENO, &tmp->buffer[i], tmp->nbytes - i); |
| 432 | |
| 433 | for (tmp = tmp->next; tmp; tmp = tmp->next) |
| 434 | XWRITE (STDOUT_FILENO, tmp->buffer, tmp->nbytes); |
| 435 | |
| 436 | free_cbuffers: |
| 437 | while (first) |
| 438 | { |
| 439 | tmp = first->next; |
| 440 | free ((char *) first); |
| 441 | first = tmp; |
| 442 | } |
| 443 | return errors; |
| 444 | } |
| 445 | |
| 446 | /* Skip N_BYTES characters from the start of pipe FD, and print |
| 447 | any extra characters that were read beyond that. |
| 448 | Return 1 on error, 0 if ok. */ |
| 449 | |
| 450 | static int |
| 451 | start_bytes (const char *filename, int fd, off_t n_bytes) |
| 452 | { |
| 453 | char buffer[BUFSIZ]; |
| 454 | int bytes_read = 0; |
| 455 | |
| 456 | while (n_bytes > 0 && (bytes_read = safe_read (fd, buffer, BUFSIZ)) > 0) |
| 457 | n_bytes -= bytes_read; |
| 458 | if (bytes_read == -1) |
| 459 | { |
| 460 | error (0, errno, "%s", filename); |
| 461 | return 1; |
| 462 | } |
| 463 | else if (n_bytes < 0) |
| 464 | XWRITE (STDOUT_FILENO, &buffer[bytes_read + n_bytes], -n_bytes); |
| 465 | return 0; |
| 466 | } |
| 467 | |
| 468 | /* Skip N_LINES lines at the start of file or pipe FD, and print |
| 469 | any extra characters that were read beyond that. |
| 470 | Return 1 on error, 0 if ok. */ |
| 471 | |
| 472 | static int |
| 473 | start_lines (const char *filename, int fd, long int n_lines) |
| 474 | { |
| 475 | char buffer[BUFSIZ]; |
| 476 | int bytes_read = 0; |
| 477 | int bytes_to_skip = 0; |
| 478 | |
| 479 | while (n_lines && (bytes_read = safe_read (fd, buffer, BUFSIZ)) > 0) |
| 480 | { |
| 481 | bytes_to_skip = 0; |
| 482 | while (bytes_to_skip < bytes_read) |
| 483 | if (buffer[bytes_to_skip++] == '\n' && --n_lines == 0) |
| 484 | break; |
| 485 | } |
| 486 | if (bytes_read == -1) |
| 487 | { |
| 488 | error (0, errno, "%s", filename); |
| 489 | return 1; |
| 490 | } |
| 491 | else if (bytes_to_skip < bytes_read) |
| 492 | { |
| 493 | XWRITE (STDOUT_FILENO, &buffer[bytes_to_skip], |
| 494 | bytes_read - bytes_to_skip); |
| 495 | } |
| 496 | return 0; |
| 497 | } |
| 498 | |
| 499 | /* Display file FILENAME from the current position in FD to the end. |
| 500 | If `forever' is nonzero, keep reading from the end of the file |
| 501 | until killed. Return the number of bytes read from the file. */ |
| 502 | |
| 503 | static long |
| 504 | dump_remainder (const char *filename, int fd) |
| 505 | { |
| 506 | char buffer[BUFSIZ]; |
| 507 | int bytes_read; |
| 508 | long total; |
| 509 | |
| 510 | total = 0; |
| 511 | output: |
| 512 | while ((bytes_read = safe_read (fd, buffer, BUFSIZ)) > 0) |
| 513 | { |
| 514 | XWRITE (STDOUT_FILENO, buffer, bytes_read); |
| 515 | total += bytes_read; |
| 516 | } |
| 517 | if (bytes_read == -1) |
| 518 | error (EXIT_FAILURE, errno, "%s", filename); |
| 519 | if (forever) |
| 520 | { |
| 521 | fflush (stdout); |
| 522 | sleep (1); |
| 523 | goto output; |
| 524 | } |
| 525 | else |
| 526 | { |
| 527 | if (forever_multiple) |
| 528 | fflush (stdout); |
| 529 | } |
| 530 | |
| 531 | return total; |
| 532 | } |
| 533 | |
| 534 | /* Tail NFILES (>1) files forever until killed. The file names are in |
| 535 | NAMES. The open file descriptors are in `file_descs', and the size |
| 536 | at which we stopped tailing them is in `file_sizes'. We loop over |
| 537 | each of them, doing an fstat to see if they have changed size. If |
| 538 | none of them have changed size in one iteration, we sleep for a |
| 539 | second and try again. We do this until the user interrupts us. */ |
| 540 | |
| 541 | static void |
| 542 | tail_forever (char **names, int nfiles) |
| 543 | { |
| 544 | int last; |
| 545 | |
| 546 | last = -1; |
| 547 | |
| 548 | while (1) |
| 549 | { |
| 550 | int i; |
| 551 | int changed; |
| 552 | |
| 553 | changed = 0; |
| 554 | for (i = 0; i < nfiles; i++) |
| 555 | { |
| 556 | struct stat stats; |
| 557 | |
| 558 | if (file_descs[i] < 0) |
| 559 | continue; |
| 560 | if (fstat (file_descs[i], &stats) < 0) |
| 561 | { |
| 562 | error (0, errno, "%s", names[i]); |
| 563 | file_descs[i] = -1; |
| 564 | continue; |
| 565 | } |
| 566 | if (stats.st_size == file_sizes[i]) |
| 567 | continue; |
| 568 | |
| 569 | /* This file has changed size. Print out what we can, and |
| 570 | then keep looping. */ |
| 571 | |
| 572 | changed = 1; |
| 573 | |
| 574 | if (stats.st_size < file_sizes[i]) |
| 575 | { |
| 576 | write_header (names[i], "file truncated"); |
| 577 | last = i; |
| 578 | lseek (file_descs[i], stats.st_size, SEEK_SET); |
| 579 | file_sizes[i] = stats.st_size; |
| 580 | continue; |
| 581 | } |
| 582 | |
| 583 | if (i != last) |
| 584 | { |
| 585 | if (print_headers) |
| 586 | write_header (names[i], NULL); |
| 587 | last = i; |
| 588 | } |
| 589 | file_sizes[i] += dump_remainder (names[i], file_descs[i]); |
| 590 | } |
| 591 | |
| 592 | /* If none of the files changed size, sleep. */ |
| 593 | if (! changed) |
| 594 | sleep (1); |
| 595 | } |
| 596 | } |
| 597 | |
| 598 | /* Output the last N_BYTES bytes of file FILENAME open for reading in FD. |
| 599 | Return 0 if successful, 1 if an error occurred. */ |
| 600 | |
| 601 | static int |
| 602 | tail_bytes (const char *filename, int fd, off_t n_bytes) |
| 603 | { |
| 604 | struct stat stats; |
| 605 | |
| 606 | /* FIXME: resolve this like in dd.c. */ |
| 607 | /* Use fstat instead of checking for errno == ESPIPE because |
| 608 | lseek doesn't work on some special files but doesn't return an |
| 609 | error, either. */ |
| 610 | if (fstat (fd, &stats)) |
| 611 | { |
| 612 | error (0, errno, "%s", filename); |
| 613 | return 1; |
| 614 | } |
| 615 | |
| 616 | if (from_start) |
| 617 | { |
| 618 | if (S_ISREG (stats.st_mode)) |
| 619 | lseek (fd, n_bytes, SEEK_CUR); |
| 620 | else if (start_bytes (filename, fd, n_bytes)) |
| 621 | return 1; |
| 622 | dump_remainder (filename, fd); |
| 623 | } |
| 624 | else |
| 625 | { |
| 626 | if (S_ISREG (stats.st_mode)) |
| 627 | { |
| 628 | off_t current_pos, end_pos; |
| 629 | size_t bytes_remaining; |
| 630 | |
| 631 | if ((current_pos = lseek (fd, (off_t) 0, SEEK_CUR)) != -1 |
| 632 | && (end_pos = lseek (fd, (off_t) 0, SEEK_END)) != -1) |
| 633 | { |
| 634 | off_t diff; |
| 635 | /* Be careful here. The current position may actually be |
| 636 | beyond the end of the file. */ |
| 637 | bytes_remaining = (diff = end_pos - current_pos) < 0 ? 0 : diff; |
| 638 | } |
| 639 | else |
| 640 | { |
| 641 | error (0, errno, "%s", filename); |
| 642 | return 1; |
| 643 | } |
| 644 | |
| 645 | if (bytes_remaining <= n_bytes) |
| 646 | { |
| 647 | /* From the current position to end of file, there are no |
| 648 | more bytes than have been requested. So reposition the |
| 649 | file pointer to the incoming current position and print |
| 650 | everything after that. */ |
| 651 | lseek (fd, current_pos, SEEK_SET); |
| 652 | } |
| 653 | else |
| 654 | { |
| 655 | /* There are more bytes remaining than were requested. |
| 656 | Back up. */ |
| 657 | lseek (fd, -n_bytes, SEEK_END); |
| 658 | } |
| 659 | dump_remainder (filename, fd); |
| 660 | } |
| 661 | else |
| 662 | return pipe_bytes (filename, fd, n_bytes); |
| 663 | } |
| 664 | return 0; |
| 665 | } |
| 666 | |
| 667 | /* Output the last N_LINES lines of file FILENAME open for reading in FD. |
| 668 | Return 0 if successful, 1 if an error occurred. */ |
| 669 | |
| 670 | static int |
| 671 | tail_lines (const char *filename, int fd, long int n_lines) |
| 672 | { |
| 673 | struct stat stats; |
| 674 | off_t length; |
| 675 | |
| 676 | if (fstat (fd, &stats)) |
| 677 | { |
| 678 | error (0, errno, "%s", filename); |
| 679 | return 1; |
| 680 | } |
| 681 | |
| 682 | if (from_start) |
| 683 | { |
| 684 | if (start_lines (filename, fd, n_lines)) |
| 685 | return 1; |
| 686 | dump_remainder (filename, fd); |
| 687 | } |
| 688 | else |
| 689 | { |
| 690 | /* Use file_lines only if FD refers to a regular file with |
| 691 | its file pointer positioned at beginning of file. */ |
| 692 | /* FIXME: adding the lseek conjunct is a kludge. |
| 693 | Once there's a reasonable test suite, fix the true culprit: |
| 694 | file_lines. file_lines shouldn't presume that the input |
| 695 | file pointer is initially positioned to beginning of file. */ |
| 696 | if (S_ISREG (stats.st_mode) |
| 697 | && lseek (fd, (off_t) 0, SEEK_CUR) == (off_t) 0) |
| 698 | { |
| 699 | length = lseek (fd, (off_t) 0, SEEK_END); |
| 700 | if (length != 0 && file_lines (filename, fd, n_lines, length)) |
| 701 | return 1; |
| 702 | dump_remainder (filename, fd); |
| 703 | } |
| 704 | else |
| 705 | return pipe_lines (filename, fd, n_lines); |
| 706 | } |
| 707 | return 0; |
| 708 | } |
| 709 | |
| 710 | /* Display the last N_UNITS units of file FILENAME, open for reading |
| 711 | in FD. |
| 712 | Return 0 if successful, 1 if an error occurred. */ |
| 713 | |
| 714 | static int |
| 715 | tail (const char *filename, int fd, off_t n_units) |
| 716 | { |
| 717 | if (count_lines) |
| 718 | return tail_lines (filename, fd, (long) n_units); |
| 719 | else |
| 720 | return tail_bytes (filename, fd, n_units); |
| 721 | } |
| 722 | |
| 723 | /* Display the last N_UNITS units of file FILENAME. |
| 724 | "-" for FILENAME means the standard input. |
| 725 | FILENUM is this file's index in the list of files the user gave. |
| 726 | Return 0 if successful, 1 if an error occurred. */ |
| 727 | |
| 728 | static int |
| 729 | tail_file (const char *filename, off_t n_units, int filenum) |
| 730 | { |
| 731 | int fd, errors; |
| 732 | struct stat stats; |
| 733 | |
| 734 | if (!strcmp (filename, "-") |
| 735 | { |
| 736 | have_read_stdin = 1; |
| 737 | filename = "standard input"; |
| 738 | if (print_headers) |
| 739 | write_header (filename, NULL); |
| 740 | errors = tail (filename, 0, n_units); |
| 741 | if (forever_multiple) |
| 742 | { |
| 743 | if (fstat (0, &stats) < 0) |
| 744 | { |
| 745 | error (0, errno, "standard input"); |
| 746 | errors = 1; |
| 747 | } |
| 748 | else if (!S_ISREG (stats.st_mode)) |
| 749 | { |
| 750 | error (0, 0, |
| 751 | "standard input: cannot follow end of non-regular file"); |
| 752 | errors = 1; |
| 753 | } |
| 754 | if (errors) |
| 755 | file_descs[filenum] = -1; |
| 756 | else |
| 757 | { |
| 758 | file_descs[filenum] = 0; |
| 759 | file_sizes[filenum] = stats.st_size; |
| 760 | } |
| 761 | } |
| 762 | } |
| 763 | else |
| 764 | { |
| 765 | /* Not standard input. */ |
| 766 | fd = open (filename, O_RDONLY); |
| 767 | if (fd == -1) |
| 768 | { |
| 769 | if (forever_multiple) |
| 770 | file_descs[filenum] = -1; |
| 771 | error (0, errno, "%s", filename); |
| 772 | errors = 1; |
| 773 | } |
| 774 | else |
| 775 | { |
| 776 | if (print_headers) |
| 777 | write_header (filename, NULL); |
| 778 | errors = tail (filename, fd, n_units); |
| 779 | if (forever_multiple) |
| 780 | { |
| 781 | if (fstat (fd, &stats) < 0) |
| 782 | { |
| 783 | error (0, errno, "%s", filename); |
| 784 | errors = 1; |
| 785 | } |
| 786 | else if (!S_ISREG (stats.st_mode)) |
| 787 | { |
| 788 | error (0, 0, "%s: cannot follow end of non-regular file", |
| 789 | filename); |
| 790 | errors = 1; |
| 791 | } |
| 792 | if (errors) |
| 793 | { |
| 794 | close (fd); |
| 795 | file_descs[filenum] = -1; |
| 796 | } |
| 797 | else |
| 798 | { |
| 799 | file_descs[filenum] = fd; |
| 800 | file_sizes[filenum] = stats.st_size; |
| 801 | } |
| 802 | } |
| 803 | else |
| 804 | { |
| 805 | if (close (fd)) |
| 806 | { |
| 807 | error (0, errno, "%s", filename); |
| 808 | errors = 1; |
| 809 | } |
| 810 | } |
| 811 | } |
| 812 | } |
| 813 | |
| 814 | return errors; |
| 815 | } |
| 816 | |
| 817 | extern int |
| 818 | tai_main (int argc, char **argv) |
| 819 | { |
| 820 | enum header_mode header_mode = multiple_files; |
| 821 | int exit_status = 0; |
| 822 | /* If from_start, the number of items to skip before printing; otherwise, |
| 823 | the number of items at the end of the file to print. Initially, -1 |
| 824 | means the value has not been set. */ |
| 825 | off_t n_units = -1; |
| 826 | long int tmp_long; |
| 827 | int c; /* Option character. */ |
| 828 | int n_files; |
| 829 | char **file; |
| 830 | |
| 831 | program_name = argv[0]; |
| 832 | have_read_stdin = 0; |
| 833 | count_lines = 1; |
| 834 | forever = forever_multiple = from_start = print_headers = 0; |
| 835 | |
| 836 | if (argc > 1 |
| 837 | && ((argv[1][0] == '-' && ISDIGIT (argv[1][1])) |
| 838 | || (argv[1][0] == '+' && (ISDIGIT (argv[1][1]) |
| 839 | || argv[1][1] == 0)))) |
| 840 | { |
| 841 | /* Old option syntax: a dash or plus, one or more digits (zero digits |
| 842 | are acceptable with a plus), and one or more option letters. */ |
| 843 | if (argv[1][0] == '+') |
| 844 | from_start = 1; |
| 845 | if (argv[1][1] != '\0') |
| 846 | { |
| 847 | strtol_error s_err; |
| 848 | char *p; |
| 849 | |
| 850 | s_err = xstrtol (++argv[1], &p, 0, &tmp_long, "bkm"); |
| 851 | n_units = tmp_long; |
| 852 | if (s_err == LONGINT_OVERFLOW) |
| 853 | { |
| 854 | STRTOL_FATAL_ERROR (argv[1], "argument", s_err); |
| 855 | } |
| 856 | |
| 857 | /* If a [bkm] suffix was given then count bytes, not lines. */ |
| 858 | if (p[-1] == 'b' || p[-1] == 'k' || p[-1] == 'm') |
| 859 | count_lines = 0; |
| 860 | |
| 861 | /* Parse any appended option letters. */ |
| 862 | while (*p) |
| 863 | { |
| 864 | switch (*p) |
| 865 | { |
| 866 | case 'c': |
| 867 | /* Interpret N_UNITS as # of bytes. */ |
| 868 | count_lines = 0; |
| 869 | break; |
| 870 | |
| 871 | case 'f': |
| 872 | forever = 1; |
| 873 | break; |
| 874 | |
| 875 | case 'l': |
| 876 | count_lines = 1; |
| 877 | break; |
| 878 | |
| 879 | case 'q': |
| 880 | header_mode = never; |
| 881 | break; |
| 882 | |
| 883 | case 'v': |
| 884 | header_mode = always; |
| 885 | break; |
| 886 | |
| 887 | default: |
| 888 | error (0, 0, "unrecognized option '%c'", *p); |
| 889 | usage (tail_usage); |
| 890 | } |
| 891 | ++p; |
| 892 | } |
| 893 | } |
| 894 | /* Make the options we just parsed invisible to getopt. */ |
| 895 | argv[1] = argv[0]; |
| 896 | argv++; |
| 897 | argc--; |
| 898 | } |
| 899 | |
| 900 | if (show_version) |
| 901 | { |
| 902 | printf ("tail - %s\n", PACKAGE_VERSION); |
| 903 | exit (EXIT_SUCCESS); |
| 904 | } |
| 905 | |
| 906 | if (show_help) |
| 907 | usage (tail_usage); |
| 908 | |
| 909 | if (n_units == -1) |
| 910 | n_units = DEFAULT_N_LINES; |
| 911 | |
| 912 | /* To start printing with item N_UNITS from the start of the file, skip |
| 913 | N_UNITS - 1 items. `tail +0' is actually meaningless, but for Unix |
| 914 | compatibility it's treated the same as `tail +1'. */ |
| 915 | if (from_start) |
| 916 | { |
| 917 | if (n_units) |
| 918 | --n_units; |
| 919 | } |
| 920 | |
| 921 | n_files = argc - optind; |
| 922 | file = argv + optind; |
| 923 | |
| 924 | if (n_files > 1 && forever) |
| 925 | { |
| 926 | forever_multiple = 1; |
| 927 | forever = 0; |
| 928 | file_descs = (int *) xmalloc (n_files * sizeof (int)); |
| 929 | file_sizes = (off_t *) xmalloc (n_files * sizeof (off_t)); |
| 930 | } |
| 931 | |
| 932 | if (header_mode == always |
| 933 | || (header_mode == multiple_files && n_files > 1)) |
| 934 | print_headers = 1; |
| 935 | |
| 936 | if (n_files == 0) |
| 937 | { |
| 938 | exit_status |= tail_file ("-", n_units, 0); |
| 939 | } |
| 940 | else |
| 941 | { |
| 942 | int i; |
| 943 | for (i = 0; i < n_files; i++) |
| 944 | exit_status |= tail_file (file[i], n_units, i); |
| 945 | |
| 946 | if (forever_multiple) |
| 947 | tail_forever (file, n_files); |
| 948 | } |
| 949 | |
| 950 | if (have_read_stdin && close (0) < 0) |
| 951 | error (EXIT_FAILURE, errno, "-"); |
| 952 | if (fclose (stdout) == EOF) |
| 953 | error (EXIT_FAILURE, errno, "write error"); |
| 954 | exit (exit_status == 0 ? EXIT_SUCCESS : EXIT_FAILURE); |
| 955 | } |