src/head.c

   1 /* head -- output first part of file(s)
   2    Copyright (C) 89, 90, 91, 1995-2000 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 Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* Options: (see usage)
  19    Reads from standard input if no files are given or when a filename of
  20    ``-'' is encountered.
  21    By default, filename headers are printed only if more than one file
  22    is given.
  23    By default, prints the first 10 lines (head -n 10).
  24
  25    David MacKenzie <djm@gnu.ai.mit.edu> */
  26
  27 #include <config.h>
  28
  29 #include <stdio.h>
  30 #include <getopt.h>
  31 #include <sys/types.h>
  32 #include "system.h"
  33 #include "closeout.h"
  34 #include "error.h"
  35 #include "xstrtol.h"
  36 #include "safe-read.h"
  37
  38 /* The official name of this program (e.g., no `g' prefix).  */
  39 #define PROGRAM_NAME "head"
  40
  41 #define AUTHORS "David MacKenzie"
  42
  43 /* Number of lines/chars/blocks to head. */
  44 #define DEFAULT_NUMBER 10
  45
  46 /* Size of atomic reads. */
  47 #define BUFSIZE (512 * 8)
  48
  49 /* If nonzero, print filename headers. */
  50 static int print_headers;
  51
  52 /* When to print the filename banners. */
  53 enum header_mode
  54 {
  55   multiple_files, always, never
  56 };
  57
  58 /* The name this program was run with. */
  59 char *program_name;
  60
  61 /* Have we ever read standard input?  */
  62 static int have_read_stdin;
  63
  64 static struct option const long_options[] =
  65 {
  66   {"bytes", required_argument, NULL, 'c'},
  67   {"lines", required_argument, NULL, 'n'},
  68   {"quiet", no_argument, NULL, 'q'},
  69   {"silent", no_argument, NULL, 'q'},
  70   {"verbose", no_argument, NULL, 'v'},
  71   {GETOPT_HELP_OPTION_DECL},
  72   {GETOPT_VERSION_OPTION_DECL},
  73   {NULL, 0, NULL, 0}
  74 };
  75
  76 void
  77 usage (int status)
  78 {
  79   if (status != 0)
  80     fprintf (stderr, _("Try `%s --help' for more information.\n"),
  81              program_name);
  82   else
  83     {
  84       printf (_("\
  85 Usage: %s [OPTION]... [FILE]...\n\
  86 "),
  87               program_name);
  88       printf (_("\
  89 Print first 10 lines of each FILE to standard output.\n\
  90 With more than one FILE, precede each with a header giving the file name.\n\
  91 With no FILE, or when FILE is -, read standard input.\n\
  92 \n\
  93   -c, --bytes=SIZE         print first SIZE bytes\n\
  94   -n, --lines=NUMBER       print first NUMBER lines instead of first 10\n\
  95   -q, --quiet, --silent    never print headers giving file names\n\
  96   -v, --verbose            always print headers giving file names\n\
  97       --help               display this help and exit\n\
  98       --version            output version information and exit\n\
  99 \n\
 100 SIZE may have a multiplier suffix: b for 512, k for 1K, m for 1 Meg.\n\
 101 If -VALUE is used as first OPTION, read -c VALUE when one of\n\
 102 multipliers bkm follows concatenated, else read -n VALUE.\n\
 103 "));
 104       puts (_("\nReport bugs to <bug-textutils@gnu.org>."));
 105     }
 106   exit (status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
 107 }
 108
 109 static void
 110 write_header (const char *filename)
 111 {
 112   static int first_file = 1;
 113
 114   printf ("%s==> %s <==\n", (first_file ? "" : "\n"), filename);
 115   first_file = 0;
 116 }
 117
 118 static int
 119 head_bytes (const char *filename, int fd, uintmax_t bytes_to_write)
 120 {
 121   char buffer[BUFSIZE];
 122   int bytes_read;
 123
 124   /* Need BINARY I/O for the byte counts to be accurate.  */
 125   SET_BINARY2 (fd, fileno (stdout));
 126
 127   while (bytes_to_write)
 128     {
 129       bytes_read = safe_read (fd, buffer, BUFSIZE);
 130       if (bytes_read < 0)
 131         {
 132           error (0, errno, "%s", filename);
 133           return 1;
 134         }
 135       if (bytes_read == 0)
 136         break;
 137       if (bytes_read > bytes_to_write)
 138         bytes_read = bytes_to_write;
 139       if (fwrite (buffer, 1, bytes_read, stdout) == 0)
 140         error (EXIT_FAILURE, errno, _("write error"));
 141       bytes_to_write -= bytes_read;
 142     }
 143   return 0;
 144 }
 145
 146 static int
 147 head_lines (const char *filename, int fd, uintmax_t lines_to_write)
 148 {
 149   char buffer[BUFSIZE];
 150
 151   /* Need BINARY I/O for the byte counts to be accurate.  */
 152   SET_BINARY2 (fd, fileno (stdout));
 153
 154   while (lines_to_write)
 155     {
 156       int bytes_read = safe_read (fd, buffer, BUFSIZE);
 157       int bytes_to_write = 0;
 158
 159       if (bytes_read < 0)
 160         {
 161           error (0, errno, "%s", filename);
 162           return 1;
 163         }
 164       if (bytes_read == 0)
 165         break;
 166       while (bytes_to_write < bytes_read)
 167         if (buffer[bytes_to_write++] == '\n' && --lines_to_write == 0)
 168           break;
 169       if (fwrite (buffer, 1, bytes_to_write, stdout) == 0)
 170         error (EXIT_FAILURE, errno, _("write error"));
 171     }
 172   return 0;
 173 }
 174
 175 static int
 176 head (const char *filename, int fd, uintmax_t n_units, int count_lines)
 177 {
 178   if (print_headers)
 179     write_header (filename);
 180
 181   if (count_lines)
 182     return head_lines (filename, fd, n_units);
 183   else
 184     return head_bytes (filename, fd, n_units);
 185 }
 186
 187 static int
 188 head_file (const char *filename, uintmax_t n_units, int count_lines)
 189 {
 190   int fd;
 191
 192   if (STREQ (filename, "-"))
 193     {
 194       have_read_stdin = 1;
 195       return head (_("standard input"), STDIN_FILENO, n_units, count_lines);
 196     }
 197   else
 198     {
 199       fd = open (filename, O_RDONLY);
 200       if (fd >= 0)
 201         {
 202           int errors;
 203
 204           errors = head (filename, fd, n_units, count_lines);
 205           if (close (fd) == 0)
 206             return errors;
 207         }
 208       error (0, errno, "%s", filename);
 209       return 1;
 210     }
 211 }
 212
 213 /* Convert a string of decimal digits, N_STRING, with a single, optional suffix
 214    character (b, k, or m) to an integral value.  Upon successful conversion,
 215    return that value.  If it cannot be converted, give a diagnostic and exit.
 216    COUNT_LINES indicates whether N_STRING is a number of bytes or a number
 217    of lines.  It is used solely to give a more specific diagnostic.  */
 218
 219 static uintmax_t
 220 string_to_integer (int count_lines, const char *n_string)
 221 {
 222   strtol_error s_err;
 223   uintmax_t n;
 224
 225   s_err = xstrtoumax (n_string, NULL, 10, &n, "bkm");
 226
 227   if (s_err == LONGINT_INVALID)
 228     {
 229       error (EXIT_FAILURE, 0, "%s: %s", n_string,
 230              (count_lines
 231               ? _("invalid number of lines")
 232               : _("invalid number of bytes")));
 233     }
 234
 235   if (s_err != LONGINT_OK)
 236     {
 237       error (EXIT_FAILURE, 0,
 238              _("%s: %s is so large that it is not representable"), n_string,
 239              count_lines ? _("number of lines") : _("number of bytes"));
 240     }
 241
 242   return n;
 243 }
 244
 245 int
 246 main (int argc, char **argv)
 247 {
 248   enum header_mode header_mode = multiple_files;
 249   int exit_status = 0;
 250   char *n_string;
 251   int c;
 252
 253   /* Number of items to print. */
 254   uintmax_t n_units = DEFAULT_NUMBER;
 255
 256   /* If nonzero, interpret the numeric argument as the number of lines.
 257      Otherwise, interpret it as the number of bytes.  */
 258   int count_lines = 1;
 259
 260   program_name = argv[0];
 261   setlocale (LC_ALL, "");
 262   bindtextdomain (PACKAGE, LOCALEDIR);
 263   textdomain (PACKAGE);
 264
 265   atexit (close_stdout);
 266
 267   have_read_stdin = 0;
 268
 269   print_headers = 0;
 270
 271   if (argc > 1 && argv[1][0] == '-' && ISDIGIT (argv[1][1]))
 272     {
 273       char *end_n_string;
 274       char multiplier_char = 0;
 275
 276       n_string = &argv[1][1];
 277
 278       /* Old option syntax; a dash, one or more digits, and one or
 279          more option letters.  Move past the number. */
 280       for (++argv[1]; ISDIGIT (*argv[1]); ++argv[1])
 281         {
 282           /* empty */
 283         }
 284
 285       /* Pointer to the byte after the last digit.  */
 286       end_n_string = argv[1];
 287
 288       /* Parse any appended option letters. */
 289       while (*argv[1])
 290         {
 291           switch (*argv[1])
 292             {
 293             case 'c':
 294               count_lines = 0;
 295               multiplier_char = 0;
 296               break;
 297
 298             case 'b':
 299             case 'k':
 300             case 'm':
 301               count_lines = 0;
 302               multiplier_char = *argv[1];
 303               break;
 304
 305             case 'l':
 306               count_lines = 1;
 307               break;
 308
 309             case 'q':
 310               header_mode = never;
 311               break;
 312
 313             case 'v':
 314               header_mode = always;
 315               break;
 316
 317             default:
 318               error (0, 0, _("unrecognized option `-%c'"), *argv[1]);
 319               usage (1);
 320             }
 321           ++argv[1];
 322         }
 323
 324       /* Append the multiplier character (if any) onto the end of
 325          the digit string.  Then add NUL byte if necessary.  */
 326       *end_n_string = multiplier_char;
 327       if (multiplier_char)
 328         *(++end_n_string) = 0;
 329
 330       n_units = string_to_integer (count_lines, n_string);
 331
 332       /* Make the options we just parsed invisible to getopt. */
 333       argv[1] = argv[0];
 334       argv++;
 335       argc--;
 336
 337       /* FIXME: allow POSIX options if there were obsolescent ones?  */
 338
 339     }
 340
 341   while ((c = getopt_long (argc, argv, "c:n:qv", long_options, NULL)) != -1)
 342     {
 343       switch (c)
 344         {
 345         case 0:
 346           break;
 347
 348         case 'c':
 349           count_lines = 0;
 350           n_units = string_to_integer (count_lines, optarg);
 351           break;
 352
 353         case 'n':
 354           count_lines = 1;
 355           n_units = string_to_integer (count_lines, optarg);
 356           break;
 357
 358         case 'q':
 359           header_mode = never;
 360           break;
 361
 362         case 'v':
 363           header_mode = always;
 364           break;
 365
 366         case_GETOPT_HELP_CHAR;
 367
 368         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 369
 370         default:
 371           usage (1);
 372         }
 373     }
 374
 375   if (header_mode == always
 376       || (header_mode == multiple_files && optind < argc - 1))
 377     print_headers = 1;
 378
 379   if (optind == argc)
 380     exit_status |= head_file ("-", n_units, count_lines);
 381
 382   for (; optind < argc; ++optind)
 383     exit_status |= head_file (argv[optind], n_units, count_lines);
 384
 385   if (have_read_stdin && close (STDIN_FILENO) < 0)
 386     error (EXIT_FAILURE, errno, "-");
 387
 388   exit (exit_status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
 389 }