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 "xstrtol.h"
  35 #include "safe-read.h"
  36
  37 /* The official name of this program (e.g., no `g' prefix).  */
  38 #define PROGRAM_NAME "head"
  39
  40 #define AUTHORS "David MacKenzie"
  41
  42 /* Number of lines/chars/blocks to head. */
  43 #define DEFAULT_NUMBER 10
  44
  45 /* Size of atomic reads. */
  46 #define BUFSIZE (512 * 8)
  47
  48 /* If nonzero, print filename headers. */
  49 static int print_headers;
  50
  51 /* When to print the filename banners. */
  52 enum header_mode
  53 {
  54   multiple_files, always, never
  55 };
  56
  57 /* The name this program was run with. */
  58 char *program_name;
  59
  60 /* Have we ever read standard input?  */
  61 static int have_read_stdin;
  62
  63 static struct option const long_options[] =
  64 {
  65   {"bytes", required_argument, NULL, 'c'},
  66   {"lines", required_argument, NULL, 'n'},
  67   {"quiet", no_argument, NULL, 'q'},
  68   {"silent", no_argument, NULL, 'q'},
  69   {"verbose", no_argument, NULL, 'v'},
  70   {GETOPT_HELP_OPTION_DECL},
  71   {GETOPT_VERSION_OPTION_DECL},
  72   {NULL, 0, NULL, 0}
  73 };
  74
  75 void
  76 usage (int status)
  77 {
  78   if (status != 0)
  79     fprintf (stderr, _("Try `%s --help' for more information.\n"),
  80              program_name);
  81   else
  82     {
  83       printf (_("\
  84 Usage: %s [OPTION]... [FILE]...\n\
  85 "),
  86               program_name);
  87       printf (_("\
  88 Print first 10 lines of each FILE to standard output.\n\
  89 With more than one FILE, precede each with a header giving the file name.\n\
  90 With no FILE, or when FILE is -, read standard input.\n\
  91 \n\
  92   -c, --bytes=SIZE         print first SIZE bytes\n\
  93   -n, --lines=NUMBER       print first NUMBER lines instead of first 10\n\
  94   -q, --quiet, --silent    never print headers giving file names\n\
  95   -v, --verbose            always print headers giving file names\n\
  96       --help               display this help and exit\n\
  97       --version            output version information and exit\n\
  98 \n\
  99 SIZE may have a multiplier suffix: b for 512, k for 1K, m for 1 Meg.\n\
 100 If -VALUE is used as first OPTION, read -c VALUE when one of\n\
 101 multipliers bkm follows concatenated, else read -n VALUE.\n\
 102 "));
 103       puts (_("\nReport bugs to <bug-textutils@gnu.org>."));
 104     }
 105   exit (status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
 106 }
 107
 108 static void
 109 write_header (const char *filename)
 110 {
 111   static int first_file = 1;
 112
 113   printf ("%s==> %s <==\n", (first_file ? "" : "\n"), filename);
 114   first_file = 0;
 115 }
 116
 117 static int
 118 head_bytes (const char *filename, int fd, uintmax_t bytes_to_write)
 119 {
 120   char buffer[BUFSIZE];
 121   int bytes_read;
 122
 123   /* Need BINARY I/O for the byte counts to be accurate.  */
 124   SET_BINARY2 (fd, fileno (stdout));
 125
 126   while (bytes_to_write)
 127     {
 128       bytes_read = safe_read (fd, buffer, BUFSIZE);
 129       if (bytes_read < 0)
 130         {
 131           error (0, errno, "%s", filename);
 132           return 1;
 133         }
 134       if (bytes_read == 0)
 135         break;
 136       if (bytes_read > bytes_to_write)
 137         bytes_read = bytes_to_write;
 138       if (fwrite (buffer, 1, bytes_read, stdout) == 0)
 139         error (EXIT_FAILURE, errno, _("write error"));
 140       bytes_to_write -= bytes_read;
 141     }
 142   return 0;
 143 }
 144
 145 static int
 146 head_lines (const char *filename, int fd, uintmax_t lines_to_write)
 147 {
 148   char buffer[BUFSIZE];
 149
 150   /* Need BINARY I/O for the byte counts to be accurate.  */
 151   SET_BINARY2 (fd, fileno (stdout));
 152
 153   while (lines_to_write)
 154     {
 155       int bytes_read = safe_read (fd, buffer, BUFSIZE);
 156       int bytes_to_write = 0;
 157
 158       if (bytes_read < 0)
 159         {
 160           error (0, errno, "%s", filename);
 161           return 1;
 162         }
 163       if (bytes_read == 0)
 164         break;
 165       while (bytes_to_write < bytes_read)
 166         if (buffer[bytes_to_write++] == '\n' && --lines_to_write == 0)
 167           break;
 168       if (fwrite (buffer, 1, bytes_to_write, stdout) == 0)
 169         error (EXIT_FAILURE, errno, _("write error"));
 170     }
 171   return 0;
 172 }
 173
 174 static int
 175 head (const char *filename, int fd, uintmax_t n_units, int count_lines)
 176 {
 177   if (count_lines)
 178     return head_lines (filename, fd, n_units);
 179   else
 180     return head_bytes (filename, fd, n_units);
 181 }
 182
 183 static int
 184 head_file (const char *filename, uintmax_t n_units, int count_lines)
 185 {
 186   int fd;
 187
 188   if (STREQ (filename, "-"))
 189     {
 190       have_read_stdin = 1;
 191       filename = _("standard input");
 192       if (print_headers)
 193         write_header (filename);
 194       return head (filename, 0, n_units, count_lines);
 195     }
 196   else
 197     {
 198       fd = open (filename, O_RDONLY);
 199       if (fd >= 0)
 200         {
 201           int errors;
 202
 203           if (print_headers)
 204             write_header (filename);
 205           errors = head (filename, fd, n_units, count_lines);
 206           if (close (fd) == 0)
 207             return errors;
 208         }
 209       error (0, errno, "%s", filename);
 210       return 1;
 211     }
 212 }
 213
 214 /* Convert a string of digits, N_STRING, with a single, optional suffix
 215    character (b, k, or m) to an integral value.  Upon successful conversion,
 216    return that value.  If it cannot be converted, give a diagnostic and exit.
 217    COUNT_LINES indicates whether N_STRING is a number of bytes or a number
 218    of lines.  It is used solely to give a more specific diagnostic.  */
 219
 220 static uintmax_t
 221 string_to_integer (int count_lines, const char *n_string)
 222 {
 223   strtol_error s_err;
 224   uintmax_t n;
 225
 226   s_err = xstrtoumax (n_string, NULL, 0, &n, "bkm");
 227
 228   if (s_err == LONGINT_INVALID)
 229     {
 230       error (EXIT_FAILURE, 0, "%s: %s", n_string,
 231              (count_lines
 232               ? _("invalid number of lines")
 233               : _("invalid number of bytes")));
 234     }
 235
 236   if (s_err != LONGINT_OK)
 237     {
 238       error (EXIT_FAILURE, 0,
 239              _("%s: %s is so large that it is not representable"), n_string,
 240              count_lines ? _("number of lines") : _("number of bytes"));
 241     }
 242
 243   return n;
 244 }
 245
 246 int
 247 main (int argc, char **argv)
 248 {
 249   enum header_mode header_mode = multiple_files;
 250   int exit_status = 0;
 251   char *n_string;
 252   int c;
 253
 254   /* Number of items to print. */
 255   uintmax_t n_units = DEFAULT_NUMBER;
 256
 257   /* If nonzero, interpret the numeric argument as the number of lines.
 258      Otherwise, interpret it as the number of bytes.  */
 259   int count_lines = 1;
 260
 261   program_name = argv[0];
 262   setlocale (LC_ALL, "");
 263   bindtextdomain (PACKAGE, LOCALEDIR);
 264   textdomain (PACKAGE);
 265
 266   have_read_stdin = 0;
 267
 268   print_headers = 0;
 269
 270   if (argc > 1 && argv[1][0] == '-' && ISDIGIT (argv[1][1]))
 271     {
 272       char *end_n_string;
 273       char multiplier_char = 0;
 274
 275       n_string = &argv[1][1];
 276
 277       /* Old option syntax; a dash, one or more digits, and one or
 278          more option letters.  Move past the number. */
 279       for (++argv[1]; ISDIGIT (*argv[1]); ++argv[1])
 280         {
 281           /* empty */
 282         }
 283
 284       /* Pointer to the byte after the last digit.  */
 285       end_n_string = argv[1];
 286
 287       /* Parse any appended option letters. */
 288       while (*argv[1])
 289         {
 290           switch (*argv[1])
 291             {
 292             case 'c':
 293               count_lines = 0;
 294               multiplier_char = 0;
 295               break;
 296
 297             case 'b':
 298             case 'k':
 299             case 'm':
 300               count_lines = 0;
 301               multiplier_char = *argv[1];
 302               break;
 303
 304             case 'l':
 305               count_lines = 1;
 306               break;
 307
 308             case 'q':
 309               header_mode = never;
 310               break;
 311
 312             case 'v':
 313               header_mode = always;
 314               break;
 315
 316             default:
 317               error (0, 0, _("unrecognized option `-%c'"), *argv[1]);
 318               usage (1);
 319             }
 320           ++argv[1];
 321         }
 322
 323       /* Append the multiplier character (if any) onto the end of
 324          the digit string.  Then add NUL byte if necessary.  */
 325       *end_n_string = multiplier_char;
 326       if (multiplier_char)
 327         *(++end_n_string) = 0;
 328
 329       n_units = string_to_integer (count_lines, n_string);
 330
 331       /* Make the options we just parsed invisible to getopt. */
 332       argv[1] = argv[0];
 333       argv++;
 334       argc--;
 335
 336       /* FIXME: allow POSIX options if there were obsolescent ones?  */
 337
 338     }
 339
 340   while ((c = getopt_long (argc, argv, "c:n:qv", long_options, NULL)) != -1)
 341     {
 342       switch (c)
 343         {
 344         case 0:
 345           break;
 346
 347         case 'c':
 348           count_lines = 0;
 349           n_units = string_to_integer (count_lines, optarg);
 350           break;
 351
 352         case 'n':
 353           count_lines = 1;
 354           n_units = string_to_integer (count_lines, optarg);
 355           break;
 356
 357         case 'q':
 358           header_mode = never;
 359           break;
 360
 361         case 'v':
 362           header_mode = always;
 363           break;
 364
 365         case_GETOPT_HELP_CHAR;
 366
 367         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 368
 369         default:
 370           usage (1);
 371         }
 372     }
 373
 374   if (header_mode == always
 375       || (header_mode == multiple_files && optind < argc - 1))
 376     print_headers = 1;
 377
 378   if (optind == argc)
 379     exit_status |= head_file ("-", n_units, count_lines);
 380
 381   for (; optind < argc; ++optind)
 382     exit_status |= head_file (argv[optind], n_units, count_lines);
 383
 384   if (have_read_stdin && close (0) < 0)
 385     error (EXIT_FAILURE, errno, "-");
 386   if (fclose (stdout) == EOF)
 387     error (EXIT_FAILURE, errno, _("write error"));
 388
 389   exit (exit_status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
 390 }