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   return (EXECUTION_SUCCESS);
  92 }
  93
  94 int
  95 head_builtin (list)
  96      WORD_LIST *list;
  97 {
  98   int nline, opt, rval;
  99   WORD_LIST *l;
 100   FILE *fp;
 101
 102   char *t;
 103
 104   munge_list (list);    /* change -num into -n num */
 105
 106   reset_internal_getopt ();
 107   nline = 10;
 108   while ((opt = internal_getopt (list, "n:")) != -1)
 109     {
 110       switch (opt)
 111         {
 112         case 'n':
 113           nline = atoi (list_optarg);
 114           if (nline <= 0)
 115             {
 116               builtin_error ("bad line count: %s", list_optarg);
 117               return (EX_USAGE);
 118             }
 119           break;
 120         default:
 121           builtin_usage ();
 122           return (EX_USAGE);
 123         }
 124     }
 125   list = loptend;
 126
 127   if (list == 0)
 128     return (file_head (stdin, nline));
 129
 130   for (rval = EXECUTION_SUCCESS, opt = 1, l = list; l; l = l->next)
 131     {
 132       fp = fopen (l->word->word, "r");
 133       if (fp == NULL)
 134         {
 135           builtin_error ("%s: %s", l->word->word, strerror (errno));
 136           continue;
 137         }
 138       if (list->next)   /* more than one file */
 139         {
 140           printf ("%s==> %s <==\n", opt ? "" : "\n", l->word->word);
 141           opt = 0;
 142         }
 143       rval = file_head (fp, nline);
 144       fclose (fp);
 145     }
 146
 147   return (rval);
 148 }
 149
 150 char *head_doc[] = {
 151         "Display lines from beginning of file.",
 152         "",
 153         "Copy the first N lines from the input files to the standard output.",
 154         "N is supplied as an argument to the `-n' option.  If N is not given,",
 155         "the first ten lines are copied.",
 156         (char *)NULL
 157 };
 158
 159 struct builtin head_struct = {
 160         "head",                 /* builtin name */
 161         head_builtin,           /* function implementing the builtin */
 162         BUILTIN_ENABLED,        /* initial flags for builtin */
 163         head_doc,               /* array of long documentation strings. */
 164         "head [-n num] [file ...]", /* usage synopsis; becomes short_doc */
 165         0                       /* reserved for internal use */
 166 };