src/head.c

   1 /* head -- output first part of file(s)
   2    Copyright (C) 89, 90, 91, 1995-1999 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 "error.h"
  34 #include "long-options.h"
  35 #include "xstrtoul.h"
  36 #include "safe-read.h"
  37
  38 /* FIXME: someday, make this really *be* `long long'.  */
  39 typedef long int U_LONG_LONG;
  40
  41 /* Number of lines/chars/blocks to head. */
  42 #define DEFAULT_NUMBER 10
  43
  44 /* Size of atomic reads. */
  45 #define BUFSIZE (512 * 8)
  46
  47 /* If nonzero, print filename headers. */
  48 static int print_headers;
  49
  50 /* When to print the filename banners. */
  51 enum header_mode
  52 {
  53   multiple_files, always, never
  54 };
  55
  56 /* The name this program was run with. */
  57 char *program_name;
  58
  59 /* Have we ever read standard input?  */
  60 static int have_read_stdin;
  61
  62 static struct option const long_options[] =
  63 {
  64   {"bytes", required_argument, NULL, 'c'},
  65   {"lines", required_argument, NULL, 'n'},
  66   {"quiet", no_argument, NULL, 'q'},
  67   {"silent", no_argument, NULL, 'q'},
  68   {"verbose", no_argument, NULL, 'v'},
  69   {NULL, 0, NULL, 0}
  70 };
  71
  72 void
  73 usage (int status)
  74 {
  75   if (status != 0)
  76     fprintf (stderr, _("Try `%s --help' for more information.\n"),
  77              program_name);
  78   else
  79     {
  80       printf (_("\
  81 Usage: %s [OPTION]... [FILE]...\n\
  82 "),
  83               program_name);
  84       printf (_("\
  85 Print first 10 lines of each FILE to standard output.\n\
  86 With more than one FILE, precede each with a header giving the file name.\n\
  87 With no FILE, or when FILE is -, read standard input.\n\
  88 \n\
  89   -c, --bytes=SIZE         print first SIZE bytes\n\
  90   -n, --lines=NUMBER       print first NUMBER lines instead of first 10\n\
  91   -q, --quiet, --silent    never print headers giving file names\n\
  92   -v, --verbose            always print headers giving file names\n\
  93       --help               display this help and exit\n\
  94       --version            output version information and exit\n\
  95 \n\
  96 SIZE may have a multiplier suffix: b for 512, k for 1K, m for 1 Meg.\n\
  97 If -VALUE is used as first OPTION, read -c VALUE when one of\n\
  98 multipliers bkm follows concatenated, else read -n VALUE.\n\
  99 "));
 100       puts (_("\nReport bugs to <bug-textutils@gnu.org>."));
 101     }
 102   exit (status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
 103 }
 104
 105 static void
 106 write_header (const char *filename)
 107 {
 108   static int first_file = 1;
 109
 110   printf ("%s==> %s <==\n", (first_file ? "" : "\n"), filename);
 111   first_file = 0;
 112 }
 113
 114 static int
 115 head_bytes (const char *filename, int fd, U_LONG_LONG bytes_to_write)
 116 {
 117   char buffer[BUFSIZE];
 118   int bytes_read;
 119
 120   /* Need BINARY I/O for the byte counts to be accurate.  */
 121   SET_BINARY2 (fd, fileno (stdout));
 122
 123   while (bytes_to_write)
 124     {
 125       bytes_read = safe_read (fd, buffer, BUFSIZE);
 126       if (bytes_read < 0)
 127         {
 128           error (0, errno, "%s", filename);
 129           return 1;
 130         }
 131       if (bytes_read == 0)
 132         break;
 133       if (bytes_read > bytes_to_write)
 134         bytes_read = bytes_to_write;
 135       if (fwrite (buffer, 1, bytes_read, stdout) == 0)
 136         error (EXIT_FAILURE, errno, _("write error"));
 137       bytes_to_write -= bytes_read;
 138     }
 139   return 0;
 140 }
 141
 142 static int
 143 head_lines (const char *filename, int fd, U_LONG_LONG lines_to_write)
 144 {
 145   char buffer[BUFSIZE];
 146   int bytes_read;
 147   int bytes_to_write;
 148
 149   /* Need BINARY I/O for the byte counts to be accurate.  */
 150   SET_BINARY2 (fd, fileno (stdout));
 151
 152   while (lines_to_write)
 153     {
 154       bytes_read = safe_read (fd, buffer, BUFSIZE);
 155       if (bytes_read < 0)
 156         {
 157           error (0, errno, "%s", filename);
 158           return 1;
 159         }
 160       if (bytes_read == 0)
 161         break;
 162       bytes_to_write = 0;
 163       while (bytes_to_write < bytes_read)
 164         if (buffer[bytes_to_write++] == '\n' && --lines_to_write == 0)
 165           break;
 166       if (fwrite (buffer, 1, bytes_to_write, stdout) == 0)
 167         error (EXIT_FAILURE, errno, _("write error"));
 168     }
 169   return 0;
 170 }
 171
 172 static int
 173 head (const char *filename, int fd, U_LONG_LONG n_units, int count_lines)
 174 {
 175   if (count_lines)
 176     return head_lines (filename, fd, n_units);
 177   else
 178     return head_bytes (filename, fd, n_units);
 179 }
 180
 181 static int
 182 head_file (const char *filename, U_LONG_LONG n_units, int count_lines)
 183 {
 184   int fd;
 185
 186   if (STREQ (filename, "-"))
 187     {
 188       have_read_stdin = 1;
 189       filename = _("standard input");
 190       if (print_headers)
 191         write_header (filename);
 192       return head (filename, 0, n_units, count_lines);
 193     }
 194   else
 195     {
 196       fd = open (filename, O_RDONLY);
 197       if (fd >= 0)
 198         {
 199           int errors;
 200
 201           if (print_headers)
 202             write_header (filename);
 203           errors = head (filename, fd, n_units, count_lines);
 204           if (close (fd) == 0)
 205             return errors;
 206         }
 207       error (0, errno, "%s", filename);
 208       return 1;
 209     }
 210 }
 211
 212 /* Convert a string of digits, N_STRING, with a single, optional suffix
 213    character (b, k, or m) to an integral value.  Upon successful conversion,
 214    return that value.  If it cannot be converted, give a diagnostic and exit.
 215    COUNT_LINES indicates whether N_STRING is a number of bytes or a number
 216    of lines.  It is used solely to give a more specific diagnostic.  */
 217
 218 static U_LONG_LONG
 219 string_to_ull (int count_lines, const char *n_string)
 220 {
 221   strtol_error s_err;
 222   unsigned long int tmp_ulong;
 223
 224   s_err = xstrtoul (n_string, NULL, 0, &tmp_ulong, "bkm");
 225
 226   if (s_err == LONGINT_INVALID)
 227     {
 228       error (EXIT_FAILURE, 0, "%s: %s", n_string,
 229              (count_lines
 230               ? _("invalid number of lines")
 231               : _("invalid number of bytes")));
 232     }
 233
 234   if (s_err != LONGINT_OK)
 235     {
 236       error (EXIT_FAILURE, 0,
 237              _("%s: %s is so large that it is not representable"), n_string,
 238              count_lines ? _("number of lines") : _("number of bytes"));
 239     }
 240
 241   return tmp_ulong;
 242 }
 243
 244 int
 245 main (int argc, char **argv)
 246 {
 247   enum header_mode header_mode = multiple_files;
 248   int exit_status = 0;
 249   char *n_string;
 250   int c;
 251
 252   /* Number of items to print. */
 253   U_LONG_LONG n_units = DEFAULT_NUMBER;
 254
 255   /* If nonzero, interpret the numeric argument as the number of lines.
 256      Otherwise, interpret it as the number of bytes.  */
 257   int count_lines = 1;
 258
 259   program_name = argv[0];
 260   setlocale (LC_ALL, "");
 261   bindtextdomain (PACKAGE, LOCALEDIR);
 262   textdomain (PACKAGE);
 263
 264   parse_long_options (argc, argv, "head", GNU_PACKAGE, VERSION,
 265                       "David MacKenzie", usage);
 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_ull (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_ull (count_lines, optarg);
 351           break;
 352
 353         case 'n':
 354           count_lines = 1;
 355           n_units = string_to_ull (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         default:
 367           usage (1);
 368         }
 369     }
 370
 371   if (header_mode == always
 372       || (header_mode == multiple_files && optind < argc - 1))
 373     print_headers = 1;
 374
 375   if (optind == argc)
 376     exit_status |= head_file ("-", n_units, count_lines);
 377
 378   for (; optind < argc; ++optind)
 379     exit_status |= head_file (argv[optind], n_units, count_lines);
 380
 381   if (have_read_stdin && close (0) < 0)
 382     error (EXIT_FAILURE, errno, "-");
 383   if (fclose (stdout) == EOF)
 384     error (EXIT_FAILURE, errno, _("write error"));
 385
 386   exit (exit_status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
 387 }