examples/loadables/head.c

   1 /* head - copy first part of files. */
   2
   3 /* See Makefile for compilation details. */
   4
   5 #include "config.h"
   6
   7 #include "bashtypes.h"
   8 #include "posixstat.h"
   9 #include "filecntl.h"
  10
  11 #if defined (HAVE_UNISTD_H)
  12 #  include <unistd.h>
  13 #endif
  14
  15 #include "bashansi.h"
  16
  17 #include <stdio.h>
  18 #include <errno.h>
  19 #include "chartypes.h"
  20
  21 #include "builtins.h"
  22 #include "shell.h"
  23 #include "bashgetopt.h"
  24
  25 #if !defined (errno)
  26 extern int errno;
  27 #endif
  28
  29 static void
  30 munge_list (list)
  31      WORD_LIST *list;
  32 {
  33   WORD_LIST *l, *nl;
  34   WORD_DESC *wd;
  35   char *arg;
  36
  37   for (l = list; l; l = l->next)
  38     {
  39       arg = l->word->word;
  40       if (arg[0] != '-' || arg[1] == '-' || (DIGIT(arg[1]) == 0))
  41         return;
  42       /* We have -[0-9]* */
  43       wd = make_bare_word (arg+1);
  44       nl = make_word_list (wd, l->next);
  45       l->word->word[1] = 'n';
  46       l->word->word[2] = '\0';
  47       l->next = nl;
  48       l = nl;   /* skip over new argument */
  49     }
  50 }
  51
  52 static int
  53 file_head (fp, cnt)
  54      FILE *fp;
  55      int cnt;
  56 {
  57   int ch;
  58
  59   while (cnt--)
  60     {
  61       while ((ch = getc (fp)) != EOF)
  62         {
  63           if (putchar (ch) == EOF)
  64             {
  65               builtin_error ("write error: %s", strerror (errno));
  66               return EXECUTION_FAILURE;
  67             }
  68           if (ch == '\n')
  69             break;
  70         }
  71     }
  72 }
  73
  74 head_builtin (list)
  75      WORD_LIST *list;
  76 {
  77   int nline, opt, rval;
  78   WORD_LIST *l;
  79   FILE *fp;
  80
  81   char *t;
  82
  83   munge_list (list);    /* change -num into -n num */
  84
  85   reset_internal_getopt ();
  86   nline = 10;
  87   while ((opt = internal_getopt (list, "n:")) != -1)
  88     {
  89       switch (opt)
  90         {
  91         case 'n':
  92           nline = atoi (list_optarg);
  93           if (nline <= 0)
  94             {
  95               builtin_error ("bad line count: %s", list_optarg);
  96               return (EX_USAGE);
  97             }
  98           break;
  99         default:
 100           builtin_usage ();
 101           return (EX_USAGE);
 102         }
 103     }
 104   list = loptend;
 105
 106   if (list == 0)
 107     return (file_head (stdin, nline));
 108
 109   for (rval = EXECUTION_SUCCESS, opt = 1, l = list; l; l = l->next)
 110     {
 111       fp = fopen (l->word->word, "r");
 112       if (fp == NULL)
 113         {
 114           builtin_error ("%s: %s", l->word->word, strerror (errno));
 115           continue;
 116         }
 117       if (list->next)   /* more than one file */
 118         {
 119           printf ("%s==> %s <==\n", opt ? "" : "\n", l->word->word);
 120           opt = 0;
 121         }
 122       rval = file_head (fp, nline);
 123       fclose (fp);
 124     }
 125
 126   return (rval);
 127 }
 128
 129 char *head_doc[] = {
 130         "Copy the first N lines from the input files to the standard output.",
 131         "N is supplied as an argument to the `-n' option.  If N is not given,",
 132         "the first ten lines are copied.",
 133         (char *)NULL
 134 };
 135
 136 struct builtin head_struct = {
 137         "head",                 /* builtin name */
 138         head_builtin,           /* function implementing the builtin */
 139         BUILTIN_ENABLED,        /* initial flags for builtin */
 140         head_doc,               /* array of long documentation strings. */
 141         "head [-n num] [file ...]", /* usage synopsis; becomes short_doc */
 142         0                       /* reserved for internal use */
 143 };