examples/loadables/head.c

   1 /* head - copy first part of files. */
   2
   3 /* See Makefile for compilation details. */
   4
   5 /*
   6    Copyright (C) 1999-2009 Free Software Foundation, Inc.
   7
   8    This file is part of GNU Bash.
   9    Bash is free software: you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation, either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    Bash is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with Bash.  If not, see <http://www.gnu.org/licenses/>.
  21 */
  22
  23 #include "config.h"
  24
  25 #include "bashtypes.h"
  26 #include "posixstat.h"
  27 #include "filecntl.h"
  28
  29 #if defined (HAVE_UNISTD_H)
  30 #  include <unistd.h>
  31 #endif
  32
  33 #include "bashansi.h"
  34
  35 #include <stdio.h>
  36 #include <errno.h>
  37 #include "chartypes.h"
  38
  39 #include "builtins.h"
  40 #include "shell.h"
  41 #include "bashgetopt.h"
  42 #include "common.h"
  43
  44 #if !defined (errno)
  45 extern int errno;
  46 #endif
  47
  48 static void
  49 munge_list (list)
  50      WORD_LIST *list;
  51 {
  52   WORD_LIST *l, *nl;
  53   WORD_DESC *wd;
  54   char *arg;
  55
  56   for (l = list; l; l = l->next)
  57     {
  58       arg = l->word->word;
  59       if (arg[0] != '-' || arg[1] == '-' || (DIGIT(arg[1]) == 0))
  60         return;
  61       /* We have -[0-9]* */
  62       wd = make_bare_word (arg+1);
  63       nl = make_word_list (wd, l->next);
  64       l->word->word[1] = 'n';
  65       l->word->word[2] = '\0';
  66       l->next = nl;
  67       l = nl;   /* skip over new argument */
  68     }
  69 }
  70
  71 static int
  72 file_head (fp, cnt)
  73      FILE *fp;
  74      int cnt;
  75 {
  76   int ch;
  77
  78   while (cnt--)
  79     {
  80       while ((ch = getc (fp)) != EOF)
  81         {
  82           if (putchar (ch) == EOF)
  83             {
  84               builtin_error ("write error: %s", strerror (errno));
  85               return EXECUTION_FAILURE;
  86             }
  87           if (ch == '\n')
  88             break;
  89         }
  90     }
  91 }
  92
  93 head_builtin (list)
  94      WORD_LIST *list;
  95 {
  96   int nline, opt, rval;
  97   WORD_LIST *l;
  98   FILE *fp;
  99
 100   char *t;
 101
 102   munge_list (list);    /* change -num into -n num */
 103
 104   reset_internal_getopt ();
 105   nline = 10;
 106   while ((opt = internal_getopt (list, "n:")) != -1)
 107     {
 108       switch (opt)
 109         {
 110         case 'n':
 111           nline = atoi (list_optarg);
 112           if (nline <= 0)
 113             {
 114               builtin_error ("bad line count: %s", list_optarg);
 115               return (EX_USAGE);
 116             }
 117           break;
 118         default:
 119           builtin_usage ();
 120           return (EX_USAGE);
 121         }
 122     }
 123   list = loptend;
 124
 125   if (list == 0)
 126     return (file_head (stdin, nline));
 127
 128   for (rval = EXECUTION_SUCCESS, opt = 1, l = list; l; l = l->next)
 129     {
 130       fp = fopen (l->word->word, "r");
 131       if (fp == NULL)
 132         {
 133           builtin_error ("%s: %s", l->word->word, strerror (errno));
 134           continue;
 135         }
 136       if (list->next)   /* more than one file */
 137         {
 138           printf ("%s==> %s <==\n", opt ? "" : "\n", l->word->word);
 139           opt = 0;
 140         }
 141       rval = file_head (fp, nline);
 142       fclose (fp);
 143     }
 144
 145   return (rval);
 146 }
 147
 148 char *head_doc[] = {
 149         "Display lines from beginning of file.",
 150         "",
 151         "Copy the first N lines from the input files to the standard output.",
 152         "N is supplied as an argument to the `-n' option.  If N is not given,",
 153         "the first ten lines are copied.",
 154         (char *)NULL
 155 };
 156
 157 struct builtin head_struct = {
 158         "head",                 /* builtin name */
 159         head_builtin,           /* function implementing the builtin */
 160         BUILTIN_ENABLED,        /* initial flags for builtin */
 161         head_doc,               /* array of long documentation strings. */
 162         "head [-n num] [file ...]", /* usage synopsis; becomes short_doc */
 163         0                       /* reserved for internal use */
 164 };